You know, i'm a sucker for monster girls, but I always feel centaurs / humans with a lower half of the animal are a gray area. Sure, you're doing it with a humanoid, but you're sticking it into the animal bit that would otherwise deem the moment beastality.

So it begs the question: Would you, or would you not? I'm 98% certain most would do it, because Mermaids fall into the same category. As long as it's intelligent, can think for themselves, and agree to it- then why the hell not?

Just follow the Jack Harkness Test.