Oh yes, I've heard my share of anti-bi slander, and mainly by gay men. They seem afraid that were they to get serious with a bi man, he'd run off and leave them in the dust for a woman. I pointed out to one friend that even if such *could* happen, why is it any worse than a gay partner jumping ship to sail with the next guy who catches his fancy (that *does* happen!).
I label myself gay, but have had the occasional opposite-sex attraction. The human spectrum of sexuality is so diverse, and I think it's a matter of accepting that as one of nature's wonders.
One friend of mine believes that everyone is bisexual to some extent; that is a hypothesis I will not touch, because I can't speak for universal human experience. I can certainly see the benefits of bisexuality--much better dating prospects!
"And though I may not know the answers, I can finally say I am free. And if the questions led me here, then I am who I was born to be." --Susan Boyle
"If all fools could fly, the sun would be eclipsed forever." --Dutch proverb