This extract from a longer article by Dieter Birnbacher (source below) argues that the preference utilitarian case for embryo research fails to take into account general feelings of moral revulsion that count aginst the practice.

http://www.bu.edu/wcp/Papers/Bioe/BioeBirn.htm

My thesis is that the purely want-regarding perspective, as exemplified by Hare and Singer, goes wrong in failing to give sufficient weight to indirect want-regarding considerations. The consideration I have in mind is the widespread emotional reaction to the practice or prospect of embryo research. As, among others, Mary Warnock has pointed out, this reaction is of a particularly intense and elementary character. It is more instinctive than considered or rational, which, however, should not tell against but rather in favour of its moral relevance. It is true, this instinctive reaction comes in various degrees. In some persons, it is no more than a slight uneasiness, in others it is a feeling of great intensity and existential import. Its core content can be described as the sentiment that human life in whatever stage of development should not be instrumentalised in that radical way in which embryos are instrumentalised in “consuming” embryo research.

This feeling is so widespread in Germany that the Constitutional Court (the Bundesverfassungsgericht) went so far as to apply the second formula of Kant’s Categorical Imperative (according to which man should not be treated as a mere means) even to the human embryo in its various abortion decisions, in spite of an ongoing controversy among jurists and philosophers about whether the early human embryo is rightfully subsumed under the constitutional concept of human dignity. This feeling also might help to explain why the belief is widespread that manipulation of the human embryo by research is a more serious violation of the principle of “Menschenwürde” than killing it, given the fact that scientific manipulation is seen as a more radically instrumentalising act than complete destruction.

It might be objected that these feelings are essentially bound up with certain moral viewpoints, and that if these viewpoints are indefensible these feelings cannot be appealed to as arguments against embryo research. Would it not be viciously circular to appeal to moral feelings of indignation, protest or shame in order to justify the moral judgements implied in these very feelings? Should one not have independent grounds for the truth of these implicit judgements in making the feelings count against the practice in question?

This objection rests on a misunderstanding. What is relevant form a want-regarding viewpoint is not the truth or adequacy of these feelings but their mere existence. What counts, from a want-regarding perspective, is nothing but the actual occurrence of these feelings, together with the fact that these feelings are stable under additional information, and that they are felt by those who have them to be of central and existential importance.
In my view, then, there are good want-regarding arguments against the practice of embryo research, even though of a purely indirect kind. They do not derive from any inherent “rights” of the human embryo, nor from its inherent normative status. Instead, they derive from the fact that this kind of practice is felt to be unacceptable to morally sensitive observers, on explicit or implicit principles which themselves cannot be endorsed on the basis of purely want-regarding principles.