When RMS is advocating for zoophilia and necrophilia (he's finally relented on pedophilia, though, after many years of also defending "consensual" pedophilia), it hurts the advocacy for his other causes. You can't effectively simultaneously champion two such disparate causes without one cause seeping into the other.
Edit: Sigh, here it is, let's trot it out again, 2006 is when he was defending pedophilia:
> I am skeptical of the claim that voluntarily pedophilia harms children. The arguments that it causes harm seem to be based on cases which aren't voluntary, which are then stretched by parents who are horrified by the idea that their little baby is maturing
https://stallman.org/archives/2006-mar-jun.html#05%20June%20...