Personhood: A Matter of Taste?

When is a person not a person and yet still a person at the same time?   

Let me put the question another way.  If sexual ethics is increasingly built on the sole foundation of consent between the parties, should child sexual abuse be legalized and even encouraged?  If, as Ivy League ethicist Peter Singer has argued (with increasing acceptance, so it seems), newborn babies are not persons and can be killed without such an act being considered murder, then could the same child be sexually abused with impunity?  And if not, why not?  Forgive the distasteful reference, but it goes to the heart of contemporary concepts of personhood.  Why would post partum killing be legitimate and sexual assault on a baby be illegitimate?  After all, if consent is the key to sexual ethics, then the fact that a newborn is not a person makes the matter of consent or even assault on a person irrelevant, as the argument for infanticide makes clear.

This question exposes the real nature of contemporary ethics.  It is not that we now randomly make up our morality as we go along.  On the contrary, there is a definite logic to contemporary secular ethical thought: it offers philosophical rationales after the fact, and thus a veneer of specious moral integrity, for judgments that are at heart aesthetic and built on little more than convenience and fashion.  In today's hierarchy of taste, abortion is fine, paedophilia not so much.  The former is clean, medical, scientific, convenient and, in the case of rape victims, loving.   The latter, even in our current world, is still regarded as perverted, dirty, cruel, selfish, and malicious.   Yet the premises of these two positions seem to stand in contradiction to each other.   The one assumes the new born child is not a person and thus not morally entitled to legal protection; the other assumes the exact opposite.

 So, when is a person not a person?  And when is a non-person a person?  Presumably when the commissars of contemporary taste determine so.  And who knows when -- or how -- they might change their minds?