I thought I'd share a (very debateable!) bit of thinky theory I was having a while ago with the wider world.
One of the reliable old debates to set gay and bi teeth on edge is the "who has it easier?" one about the LG and the BBB ends of LGB. I shall try to render it here: try to imagine the voice of The Book in Hitch Hiker's guide for this bit, and some line art graphics of people arguing, example images and all that.
Both sides of the argument are quite sure they're right.
So, I wonder if what is going on is like this: first, that the conversation above is a kind of class-based analysis, in other words, it leads to sweeping statements that are a pile of steaming piffle when it comes to actual lives. All gay men do not have the same experience of oppression, ditto all bi women, etc. Everyone's experience of oppression is complex and varies through their life and indeed the course of each day.
This might also explain why there is more support for lesbians and gay men than for bis: if you are up at the right hand end of the graph, it's probably harder to give support to others since your own needs are quite pressing. Whereas the bulge in the middle of the gay curve causes more people to think that there needs to be something and that they can find the time and energy to make it happen.
I stress, this is just a thinky exercise. I've got no research data, just a bit of a thought that came to me a while ago!