Is it not quite a black and white issue in that you either agree that parents can permanently alter the body of a child for non-medical reasons or you don't?
In all honesty, I don't see that as black and white. It is clear that throughout history and at present, humans embrace body modification, usually in relation to identification with a group. And that some of these modifications are begun in childhood. You bring up the idea of physical integrity as though it is universally valued, and get general agreement here because of the nature of the cultural backgrounds of those who come to the JREF. But I am not convinced this idea can generally be considered important when the vast majority of humans violate it. Not enough to interfere with what I consider private decisions, anyway.
Of course, at the other end of the scale are practices that are obviously harmful and 'consent' to such practices is coercive and we should interfere. FGM would be one of them.
Perhaps it's not possible to discuss how one rationally draws a line in a field of grey.
Linda