It's hard, as a straight male my whole life, to tell whether personal anti-homo feelings are completely natural or the result of an ingrained societal bias. I wonder if there's some sort of pyschological test for that.
Societal bias. "Homosexuality" and "heterosexuality" are, mostly, modern inventions. The line between "normal" and "deviant" behavior as regards relationships between the same sex has varied drastically over time and between cultures. In antiquity, such a distinction didn't even exist in many cases, and it wasn't that long ago that men kissing one another was considered perfectly in line with what we would now classify "heterosexual" behavior.
At least one axis here, alongside the gay-straight axis, is dominance behavior. One can feel dismissal or dislike towards people whose behavior registers as submissive. There are varying degrees to which gay men manifest this -- and considering whether your anti-homo feelings correlate with it can be informative -- but many definitely do.