Well I think that's currently the weakness of masculinity. In hetero-normative society, there are many things a man can do and retain his "manhood." Nowadays, male affection isn't one of them. That wasn't always the case though. Men used to be very friendly with one another.
Being bisexual also brings "manhood" into question. Too many people think that bi people don't exist. Too many women wouldn't date bisexual men. The threat and shame of being feminized is what keeps bisexual men DL, not to mention all the other implications like religion. I'm afraid the stakes are too high for men to openly be bisexual and retain the respect that a straight man would in this society. That's my take on it at least. Anyone else feels the same or different?
It's all hypocritical BS. I believe in bisexuality. Maybe they lean towards one gender more than the other, but that doesn't change the fact that they are bi-sexual.
Male bisexuality has such a taboo attached to it because male homosexuality is vilified and demonized in many cultures and religions including American culture. Since Christianity still has a toxic influence on people's attitudes toward sexuality in general, male homosexuality in particular. It shouldn't be surprising that bisexuality in men is kept quiet and frowned upon. In comparison female bisexuality and lesbianism is considered relatively benign or at least non threatening so women get a pass for same gender sexual behavior. Many straight men fetishize lesbians and bisexual women for obvious reasons.
Masculinity is far more fragile and the slightest variation of it calls you into question and judgement. From both men and women gay or straight so most SGL loving men period never come out and bisexual men also have to deal with their sexuality being questioned mostly by other SGL people saying it's really the base before the gay homerun which is terrible and forces more silence. I believe as long as a people is silent they will always be marginalized. I also second @LeMignon@Ishmal! You have to be one or the other for many there's no inbeteween so it invalidates our existence.
Cyrus-Brooks