Frankly, the fact that they were assuming it was a choice would anger me there.
I've run into a number of different theories: It was a choice, I was abused as a child, I was corrupted somehow, I am possessed by some kind of demon (seriously), I have a mental disorder, I'm just faking it to seem more interesting, I'm pretending just to annoy people.
"You chose to be gay" is the best, given the alternatives. It's still stupid and irritating, but given what they
could be saying, I'd rather be told I just randomly chose to like men.
Incidentally, the "faking it to annoy people" is my personal favourite to laugh at. Like, "oh yeah, I just decided at 13 to feel different and terrible for years and face possible bullying and torment at the hands of my peers just because I really like to annoy people. It makes so much sense!"
For the record: I don't UNDERSTAND your choice of behavior, simply because I've not been in your shoes or experienced what you're experiencing as a gay man.
That's fair. I don't understand the behaviour of straight men personally, so turn-about is fair play.
I understand straight women a bit more because at least they like men and that I can relate to if nothing else. Means I can talk about crushes with them. Trying to do that around straight guys is bound to make someone feel uncomfortable.