It was my birthday on Friday and, as often happens to people with Big Birthdays, I've been thinking about the past and how things have changed in my lifetime. A warning: gross generalisation alert. This is a broad brush look at how I remember things. It is not an Authorised History. Even by me.
1970s. At that point, all the publicity was about bi men, not bi women, due to David Bowie, glam-rock, a supposed kiss that Jagger and Bowie gave each other on stage. Androgyny - for men - was trendy. This must have had some impact on men at large, but I remember many of them being horribly sexist in a way you'd never hear now. Bi people in general were more incorporated into gay liberation - if you loved/were attracted to members of the same sex, you belonged. This seemed to apply to women too - but I never came across any bi women until the end of the decade. I just yearned. Kate Millett, see this post, didn't find it easy at all. On the other hand, this was - apparently - a decade of very active swinging and the Californian bi scene was openly a part of the sexual liberation movement.
1980s. Fun time was over. Bi men were hit pretty damn hard by the Aids pandemic that was first reported in 1981. In the US, many bi men died, including significant bi activists such as and so did some in the UK - actor Denholm Elliot, for instance. But as no one knew or knows how to define "bisexual man" or whether many individuals presenting with HIV symptoms were gay or bi, precisely how many will never be known.
It wasn't a great time for bi women either. A particular sort of feminism laid down that women should be lesbian and, if they couldn't, they were allowed a sort of guilty heterosexuality. But bisexual women were bad, traitrous, "taking energy from women to give to men" etc.
With that in mind, no wonder that this decade saw the establishment of the politicised bi community in the UK and North America.