"Repulsive" is a strong word. And yeah, if you have trouble seeing two gay men kissing, that's extreme and it's actually something you should probably work on. But it's also not surprising. There have been claims in here that "yeah gays are repulsed by heterosexual intercourse too" but they ring a little hollow. Straight sexuality is everywhere and everyone is inundated with it by an early age. I may not really be into vagina (and it's enough to shut it down), but I've been more or less desensitized to straight sex.
Meanwhile, this might seem surprising, but at a younger age I may have had a slight "stomach churning" reaction to two men kissing (I am pretty sure this did happen, I just can't remember the circumstances). Not because of the kissing itself, but because of the societal implications and growing up in a religious right home. Maybe in the same sense that I have a really hard time watching "cringe" humor, because my empathy is so strong for the fictional characters I'm supposed to be laughing at. I don't know. But maybe society's rules can also have an influence on aversion.
Emotions can be complicated. The fact that you feel them alone does not necessarily validate them, however. I don't think it's a problem to be grossed out by gay sex, at least to some degree. But I wouldn't, for example, say "vaginas are gross" around a girl because I think that would be extremely rude.