Very possibly. In fact, I’d be surprised if pedophiles weren’t born this way.
Regarding bestiality and necrophilia, I’m not so sure. I’d suspect that necrophilia at least is rather a kind of fetish.
To say the thr truth, I’ve zero issue with bestiality. We ride animals because it’s useful or just for fun, we have them dragging heavy loads, we kill them because we need their meat, or want good shoes or find them tasty, and so on…, so I don’t see what the big deal is with fucking them. It’s just a matter of eek factor IMO. So, I couldn’t care less whether people are in bestiality because they’re born this way or for any other reason. Might become legal someday if many people come to think like me. But it won’t be because some scientist discovered the “bestiality gene” or somesuch.
Regarding pedophilia, knowing that people can’t choose not to be pedophiles wouldn’t change a thing and wouldn’t make acceptable to act on such urges. We won’t accept that adults have sex with children, regardless of the reason. It doesn’t mean that pedophilia could never conceivably be socially acceptable (it has been in some cultures), but it would come from a significant social change, and in this case too, whether or not people are born with this attraction would be irrelevant.
I also doubt people will be ready to let anybody fuck cadavers, again regardless of the cause of necrophilia. In fact, it might be the strongest taboo of the three. In many places, fucking a goat would just make you the target of jokes, in some places, fucking a young boy would have been perfectly acceptable, but I don’t think there has ever been a culture where fucking a corpse would have been viewed with less than utter disgust and contempt.
To sum up, in all three cases, knowledge that people can’t help being attracted to dogs, kids or corpses won’t change a thing. Only a different cultural perception of dogs, kids and corpses “rights” or “acceptable uses” could result in such a change.