Ok, lets be objective. Science, while not 100% settled on this topic, tell us that sexual orientation is determined before birth.
http://en.wikipedia.org/wiki/B....
In other words people are born gay (or straight), If you want to provide evidence that this is not the case, feel free. That is an objective discussion of the facts.
Objective discussion doesn't allow for religious or moral arguments, since these are personal and subjective.
Assuming we accept the science, discriminating against people who are born with different sexual orientation ought to be no more acceptable than discriminating against people born with different skin color.
You are entitled to believe anything you like. (Isn't this a great country we live in!). However, if you believe that it is not "ok" to be black and say so out loud people will call you a racist. And, if you believe that it is not "ok" to be gay and say so out loud people will call you a homophobe (dumb word, I agree but it's all we have). Either way, you are a bigot.