Nope, gay thoughts can't be avoided, everyone has 'em every once in a while (If you challenge this, you are not human or sane).
Have you ever liked a girl? You can't exactly avoid affection toward her, even if you try your hardest.
Besides, if being gay was a choice, no one would be gay. Being gay would be like being the only one at your school who likes girls other than other girls. You'd be looked at as a freak. If you were beat up, picked on, and if you yourself started thinking you were a freak, you would give anything in the world to be like everyone else, which is, in this imaginary school, gay.
I like boobs and richards. See, biloveuality exists. Also, if you can convince yourself you like a certain love, wouldn't that be making yourself a new loveuality?
If you were able to like the same love, then you would have already been gay/biloveual. It's simple logic.
Besides, if you're not gay, you can't say it's a choice. You wouldn't know. It's like saying animals can't feel pain. You haven't been an animal, so you wouldn't know.