I believe that everyone deserves to be treated equally, regardless of their race, religion, gender, age, sexuality, etc.
I believe that the gender you choose to sleep with is no-one else's damn business. I also believe you shouldn't have to hide it for fear of what people will think. I believe that judging someone on the basis of this is wrong.
I believe that the typical justification given for homosexuality being "wrong" (usually religious reasons) is often flawed- take the Bible, for example. Homosexuality is listed as being wrong, yes. But then, so are a multitude of other things that are treated with nowhere near the same bile as homosexuality. If you're going to disapprove, at least disapprove consistently, people!
(NB: No disrespect intended to anyone religious, this is purely my own opinion 🙂 )
I also believe sexuality to be more fluid than most people describe it, though I don't know if that is the kind of opinion you're looking for.
Oh, and nothing makes me roll my eyes more than girls being "Bi for the guys" (Girls who will make out with each other purely for the purpose of attracting attention, often male). I've not noticed any men doing the same thing, but the same would be true in that situation. Most attention-seeking peeves me, though, it's not limited to these 😛
There's my opinions.