Yes, its a mental disorder where you choose to yield to sadistic and narcisistic urges like any beast of the field instead of behaving like a human being.
So, is it a mental disorder first, then a choice to yield or is it a choice first?
Homosexuality isn't a "beast" thing - beasts don't normally mess with their same sex, either.
About homos, I say, it may be natural (it occurs), but it AIN'T normal.