Whether it's a choice or not should be irrelevant. However, used as it is in the modern political context of "gay harassment issues", I believe we're actually doing a great disservice to the gay community by using "they didn't have the choice" as an excuse.
Maybe it's just me, but every time someone argues that we should accept gay people because they didn't have a choice, I can't stop myself thinking: "So if they had a choice, would it be okay to harass them? Would it be okay to ask them to change?". The problem is not that gay people can't _change_. The problem is that it's f*cking wrong to ask them to change. Even if they could _change_ (whatever people mean by that), it's absolutely nonsensical to ask them to.
As a society, we ask murderers to change, criminals, people generally harmful to others. But gays? Since when is it okay to criticize the choice of someone that affects nobody but this someone?
I like pizza. If that bothers anyone, should I just say: "There's nothing I can do about it, I was born this way?"