In the 1980s bisexuality was treated with hostility by many lesbian feminist activists. And there was a lot of hypocrisy, with more heterosexual activity going on in that community than was ever owned up to. Life has of course moved on since those days, and the harshness of that world was in part I think a reaction to, and symptom of, the harshness of British society under Thatcher. Incidentally, and to be fair, I must also say that some of the openly bisexual people weren't very nice either. What a bloody species we are.
The methodology of this research was one you will have heard of before - show people porn and see what makes them aroused. The 'findings' were that the supposedly bisexual guys only reacted to gay porn. I hardly know where to start with this, it raises so many issues. But here are some questions: is porn a good indication of sexual preference? Is the gender you fantasise about necessarily the gender you want to get it on with? Personally I find most porn utterly repellent, and 30% of the (male) sample failed to respond to any images at all - what does this say about their sexuality? Is the problem with porn?
I think attraction is sometimes about yearning for the unobtainable. Not merely the unobtained, but something that retreats necessarily, the closer you approach to it. Something that would just disappear if it fell into your grasp. I think conventional porn fails to deliver this side of sexuality, while slash fiction kind of panders to it, and it is hard to know what it even means in term of 'straight gay or bi'.
I think sometimes people of all sexualities can get a bit holier-than-thou about it. Perhaps Bisexual people do it by projecting their own attitudes on to everyone else and saying 'Oh, gender doesn't really matter, other things are more important'. But clearly that isn't the view ofeveryone, perhaps it's a minority view. And straight or gay people sometimes behave in a bisexual way for positive reasons (best friend feeling gloomy, want to please partner etc.) but that doesn't make them bisexual IMHO.
To sum up - human beings eh? *shakes head*
Some interesting opinions on this reseach, in Village Voice, from bi men and people who like them here.