If homophobia was as simple as an instinctive dislike of certain sex acts, you'd expect it to be constant across societies and demographics. The fact that it varies wildly by society and generation suggests it's more complicated. So yes, there is something to study.
Homophobia doesn't exist in liberal parts of society, that's the definition of liberal tolerate (not necessary respectful) of the behaviour and ideas that are different to one themselves but do not affect you. However the dislike of homosexual sex acts I suspect its extremely common but that's a different matter
And if it was a biological imperative, it's hard to justify calling people who feel it "think stupid illiberal bigots," unless they chose to act on their feelings. Or did you mean homophobic actions?
I have no problems in calling people morons who can't use the higher functions of their brains to overcome acting on their instincts.
Hating people who are different to yourself is pretty natural but since when is natural right?, human beings can do better than that