A psychologist who coined the word "homophobic" said the revulsion is precisely that.
I don't know, there's just something about the smell and sight of blood feces on my manhood, or just the smell of another man, which I almost always find nauseating. I am also nauseated by the scent of about half or more of the women around me as well.
Intimacy with another human being is something that's not easy to achieve, and that kind of intimacy with another man is just not normal. What else can you say?