YMMV, but I doubt there will be any objection to the basic premise that FGM is very, very wrong.
That said, if I may make a couple objections:
First, this one has already come up, but crimes against humanity specifically refer to actions/inactions by de facto or de jure governments. You need to show at least one government that actually is okay with FGM — and even if you do, you called FGM itself a crime against humanity.
Second, the earlier thread to which you refer had people arguing that FGM was a bad example of men oppressing women, not just “discrimination and oppression of females” in general. The specific ground for the objection was that the norms were perpetuated just as much by women as by men. You’ve started making a decent argument in this thread, but I’m not entirely convinced. Even if the original rationale has to do with devaluing women, I suspect that in operation, it has more to do with a norm being nearly universally accepted and perpetuated by men and women alike, though I’m open to being convinced otherwise. It seems to me that there would be change if large numbers of either gender demanded so. (The objection also had to do with treating “men” as a single actor capable of doing things, as opposed to a mere category of humanity, but that’s a different conversation.)