can you please explain the thought process that you specifically used to "choose" to be a heterosexual?
I don't think you'll find anything to be a revelation here, as I used a thought process that I'm sure is similar to what others use (whether they think deeply about it or not), but I'll indulge you:
I thought briefly about the plan I had for my life, what my levels of attraction to each gender were, and how others whose opinions I value would react to the decision and to me in general and then I made my decision.
As I said, other people do the same thing, some without giving it much thought, with others (like myself) thinking more deeply about it. I'm sure you did the same thing yourself, but of course you'll deny that because it doesn't fit with your views of sexuality.
At what point in your life did you consciously make this decision?
Some time in my early teens or perhaps right before that. I don't remember exactly when it occurred in terms of dates, but I do know I gave it serious thought (as I do with any important life decision).
What were the key decision points that influenced your decision?
The same ones that probably influence anyone else, to wit: My plan for my life, my various levels of attraction, and how those whose opinions I value might view my decision.
Do you personally know any gay people?
Have you explained to them how you have determined that homosexuality is a choice?
Some of them, yes. Others, no, mostly because the topic hasn't come up.
Have you asked them why they chose to be gay instead of straight?
Yes, with two people. One of them said he knew he wanted to be with men so that's who he picked. The other said her first sexual experience had been with a woman, she liked it, so she decided to stick with women - although I think she had some psychological issues that may have played a role in this, as she takes a long time to trust any men (we were in the same social group for four years before she said she felt she could trust me).