This entry from the New World Encyclopaedia very clearly explains why and how we can classify utilitarian ethics and situation ethics as both absolute and relative.  The answer is – they are absolute on the meta-ethical plane because they hold that there is a way of arbitrating between different moral theories – one absolute principle which is objective, out there to be measures (happiness/love), but they are relative theories on the normative plane as they do not hold for example that lying is always wrong.  So absolute can be contrasted with either relative or consequentialist ideas – hence the confusion students often fall in to. Note also that deontologists don’t have to be absolutists on the normative plane – WD Ross for example is a non-absolute deontologist (Kant however was an absolute deontologist!). PB

Source    http://www.newworldencyclopedia.org/entry/Absolutism

Meaning 1: Absolute v relative

“Absolutism” (or ‘moral absolutism’) refers, firstly, to a doctrine about the nature of morality (meta-ethics), according to which there are true or justifiable moral principles that have application to everyone, or at least, all moral agents (excluding infants and the mentally impaired for example). In other words, there are moral rules that apply to all people, including those who do not acknowledge these principles but live their lives in accordance with other, false, principles. Moral absolutism in this sense is committed to the existence of universal moral principles and for this reason is sometimes called universalism.

Moral absolutism in our first sense is opposed to moral relativism, which denies that there are any moral principles that have universal application. Rather, according to the relativist, moral principles apply locally, that is, only to the groups of people who accept them. In understanding the dispute between absolutism and relativism, it is important to distinguish the question of ‘’universal applicability” from ‘’universal acceptance.” The relativist does not deny that is possible (or even actual) that could be moral principles accepted by everyone. What he denies is that these principles would also apply to people who did not accept them. For example, suppose that as a result of globalization, everyone in the world came to ‘’accept” (roughly) the western moral code. (This is the moral code shaped by the influences of Judaism and Christianity and held by most people living in Europe and North America.) This would not imply the existence of any universal and absolute moral code for it would not imply that this code applied to others, such as future humans, who did not endorse this way of ethical thinking. So the relativist would argue that a moral code could be universally accepted, without being universally valid, and hence fail to be absolute.

Moral absolutism presupposes objectivism-the doctrine that moral principles are true, or justified, independently of anyone’s belief that they are true or justified. This is because conventional moral codes could not have any universal validity-for they are true only insofar as they are believed to be true. Secondly, although moral absolutism is committed to their being a universally valid set of moral principles, it is not committed to saying that anyone currently knows this universal moral code. So although a moral absolutist maintains that there is one and only one proper moral code and that everyone ought to live by it, he need not maintain that the code is known. However, it presumably must be knowable, and once it is discovered all are morally obliged to live by it. The reader is cautioned, however, that absolutists often write as though they do know some of these principles, and at least one contemporary writer characterizes absolutism in terms of ‘’knowledge” of an absolute moral code (see Cook 1999).

Many normative theories that would typically be discussed in an introductory ethics class count as species of absolutism in our first sense. For example, utilitarianism presents a theory of morality according to which actions are right when they produce more overall welfare than available alternatives. This is an absolute account of morality, for it implies that there is, in all circumstances, one correct answer as to what it is right to do. This applies to everyone, even to those who did not know about or accept the utilitarian principle. Similarly, Kant’s theory is also a species of absolutism for it holds that moral right and wrong are all ultimately determined by a basic principle of practical reason-the categorical imperative-and hence applicable to all rational agents. Utilitarianism and Kantianism are both forms of monism, the view that there is ultimately only one absolute and basic moral principle. However, not all forms of absolutism make this assumption. W.D. Ross’s theory, for example, endorses a plurality of absolute moral principles, none of which are any more basic than any other (see intuitionism). This is still an absolutist account of morality in our first sense, that is the sense opposed to relativism, because it claims universal applicability. W. D. Ross’s prima facie duties prescribe, for example, that it is always prima facie wrong to break a promise. (See also ethics, normative ethics)

Meaning 2: Absolute v consequentialist

“Absolutism” (or ‘moral absolutism) refers also to a particular type of ethical theory, that is, a normative theory according to which some actions (action-types) are absolutely forbidden. Absolutism in this sense says, for example, that it is always wrong to kill, or always wrong to lie, or always wrong to tortue another. It is important to notice, however, that absolutism is not a theory of ‘’which” actions are absolutely prohibited or required but only a theory that there ‘’are” some actions absolutely outlawed in this way. Absolutism upholds only the formal requirement that some moral principles admit of no exceptions-that there are some moral principles it is always wrong to break. This implies that it is possible to be an absolutist about any action-type whatsoever, although most absolutists argue for their position by means of torture, killing of the innocent, and so on.

Moral absolutism in this second sense is often held as opposed to consequentialism. Consequentialism is a theory according to which actions are right just in case they promote overall value in comparison with other alternatives. The upshot of this account is that no particular action (or action-type) could be absolutely wrong. For example, torturing a small child may produce more value (or less disvalue) than the killing of an entire nation.

Therefore, for a consequentialist, torturing a small child in order to save a country is permissible, if indeed not positively required. By contrast, moral absolutism holds that some actions are absolutely wrong; they could never be right no matter what consequences of failing to do them might be. So, an absolutist would say that it is morally wrong to torture a child in order to save an entire nation. Absolutism says that some actions are wrong whatever the consequences. Or again, moral absolutism about lying would say that the lying is always wrong, whatever the consequences. Consequentialism is sometimes construed as one type of absolutist moral theory: for instance, it is absolutely wrong not to act in such a way that promotes overall value.
Which actions or types of action are traditionally regarded as absolutely wrong? Historically, philosophers have been absolutists with regarded to many types of actions such as lying, adutery, and sodomy. However, in a contemporary setting, torture and executing the innocent are two of the actions most commonly held to be absolute prohibitions. And these are also the most plausible sort of cases. In fact, the United Nations Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment (1987) upholds an absolutism of this form. “No exceptional circumstances whatsoever, whether a state of war or a threat of war, internal political instability or any other public emergency, may be invoked as a justification of torture” (Article 2). This resolution says that no matter what the expected consequences of torture may be-for example, preventing New York City from being bombed by terrorists-torture is impermissible. It would be morally wrong to torture a terrorist in order to find out where a bomb was being hidden, even if the consequences of not doing so would be quite catastophic.

Given its emphasis on moral principles, and opposition to consequentialism, it may seem unclear how absolutism differs from deontology. The answer is that absolutism is a species of deontology. Absolutism endorses two claims: (1) some actions are intrinsically right or wrong; (2) the consequences of an action of this sort (e.g., lying) can never override its intrinsic rightness or wrongness. By contrast, a deontological ethical theory is committed to (1) but not to (2). All absolutist theories are therefore deontological, but not all deontological theories are absolutist.

Although deontological ethical theories are not necessarily absolutist, some important deontologists have been. Kant’s infamous discussion of the inquiring murderer suggests that he held that the deontological constraint on lying is absolute. In his infamous essay, ‘On a Supposed Right to Lie from Altruistic Motives’, Kant argues against the permissibility of lying even to a man whom one knows to be in the process of attempting a murder, going about looking for his victim. Kant saus that ‘to be truthful (honest) in all deliberations … is a sacred and absolutely commanding decree of reason, limited by no expediency.’ Kant is therefore an absolutist, for he would argue against lying under any conditions. This is what makes him an absolutist: lying is forbidden in every situation; it is never permissible to lie.

Similarly, an important contemporary deontologist, Charles Fried, endorses absolutism in the following passage: “Ordinary moral understanding, as well as many major traditions of Western moral theory, recognize that there are some things which a moral man will not do, no matter what…It is part of the idea that lying or murder are wrong, not just bad, that these are things you must not do-no matter what. They are not mere negatives that enter into a calculus to be outweighed by the good you might do or the greater harm you might avoid. Thus the norms which express deontological judgments-for example, Do not commit murder-may be said to be absolute. They do not say: ‘Avoid lying, other things being equal’, but ‘Do not lie, period’.” (Fried 1978) (See also Elizabeth Anscombe.)

Non-absolutist deontologists, such as W.D. Ross hold that one may in exceptional circumstances break deontological constraints. Ross distinguishes between prima facie duties and what he calls duties proper. The concept of a prima facie duty is the concept of a duty, which though it is a significant reason for not doing something, is not absolute, but must be weighed up against other duties. A duty proper refers to the action that must be done when all the prima facie duties have been considered and weighed. To illustrate, Ross thinks that we have duties to keep our promises, and duties of benevolence: these are, then, prima facie duties. Insofar as these prima facie duties come into conflict (and one cannot keep a promise and act with benevolence), one must decide on the basis of contextual details, which of these duties is most pressing. The action which is judged to be, all things considered, the right thing to do, is the duty proper. Ross’s theory is an example of a moderate deontology, that is, deontology without absolutism.

Further reading

Cook, J. W. 1999. Morality and Cultural Differences. New York: Oxford University Press.
Davis, Nancy. 1991. ‘Contemporary Deontology’ in A Companion to Ethics, ed. Peter Singer. Oxford: Blackwell
Rachels, J. 2006. The Elements of Moral Philosophy. McGraw Hill.