Yep. I've been told I'm just afraid to come out but "really gay," straight but pretending b/c it's trendy, making gay people look bad, indecisive, "sleeping with the enemy," and other stuff like that. Basically, some subset of the gay community doesn't believe it's possible to be neither gay nor straight, and gets angry that bisexual people can choose whether to *present* as gay or straight (which is a fundamental misunderstanding based on the idea that you pick your partners on purpose to present a given orientation). Not to mention that bi people are non-monagamous (to put it as politely as possible) and will always cheat.
It's tiring. Mind you, straight people have a lot of the same misconceptions, so I can't win...