Chamillion, that's interesting. I guess it's a matter of experience. It also really depends on the person/people you are dealing with. Overall, I think its all insecurity and/or lack of knowledge, whether they are gay, straight, trans, etc.
I really don't like the 'GLBT' umbrella term, there are too many animosities between people and too many exceptions that it just doesn't work.
As a straight MtF who is pre-transition, it is hard to fit in anywhere, really. I'm a gay guy to most, a poser ->-bleeped-<- to others, and it can be tough, knowing that you are something you can't readily express. I used to love going to gay bars, I felt like that was the only place where I could belong, but those places really don't do anything for me. I've never had a negative experience with the gay community, but I don't feel like they are my best friends either.