Bisexuality in men is often viewed as them being gay but not willing to admit it.

I'm a pansexual man married to a pansexual woman. We're both millenials.

Basically, when we were growing up, there was a perception that men who were ever attracted to other men, in any context and for any reason, were considered fully gay, which at the time meant bullying, being ostracized, threats of violence, and generally being treated as a lesser by your peers.

This waned somewhat as we got to high school and disappeared for the most part some time in the mid 2010s (so, well after graduation), but the cultural scar is still there.

Even now I'd call myself mostly-closeted. People from my generation and older will treat (or at least historically have treated) a man as if he's gay and in-denial even if he's like a solid 2 on the Kinsey scale. That's annoying in-itself, but the scars of how our culture was when I was growing up make it a deeply frightening prospect. I have no idea how many friends I'd lose. I hope it'd be zero since I try to pick good people, but who knows?

Being old sucks. Don't let the olds lie and say the culture was better back in the day. It wasn't. They either floated by with crazy privilege or decided their emotionally stunting trauma was a good thing.

The stifling of men's sexuality is tied in large part to a patriarchal system that places a very narrow version of masculinity at the top of a pyramid.

For men to be openly bi/pan/gay means that they lose social status because anything percieved as feminine degrades your value as a "real man". A lot of men might not think of it in those terms, but that's what underlies the fear that keeps men in line -- the fear that they have to sacrifice social position to be who they are openly.

This is why I always hold that feminism is good for men too, as it creates a path towards a world where both feminine and masculine characteristics aren't subject to these stupid restrictions and definitions designed to maintain control over others.