You seem to be a similar age to me, so have a similar response to my own.

But to add to your answer; for me in my younger years, it was primarily the fear of being othered by my peers. Being gay was seen as the worst thing a man could be, ergo, being seen as gay by my peers would have been the worst thing. So I'd overcorrect with homophobia.

In our defence (my peers and I, I mean), we were also in the midst of the AIDS crisis, where the news would keep bringing us stories of how many gay men were dying because they were having sex with each other. That's legitimately scary when you're young, just beginning to understand what sex is, and that you like the idea of it.

But in the interim I've grown up and moved into a mental space where I'm less of a prick.

For the past couple of years I've marched in the two pride marches local to me as a fully paid up supported of the LGBTQ+ community, not least because these days I don't really consider myself to be straight anyway. I'm just a bloke-shaped person who likes to experience sex with other people, regardless of their junk.