Your environment isn't limited to the family you live with. All those gay and bi friends of yours are also a part of your environment. I'm not saying being around a bunch of homos is going to make some dude want to put his dong in a guy's butt, but I think environmental influences help you reach that end point. These influences don't have to be huge things either, they could be very small seemingly insignificant things that you don't realize are changing your perspective of the world.

But they could be a big thing. I really do believe the home environment you live in can have an impact on your personality (which encompasses sexuality). I think living in a straight average household and growing up their would make you more likely to be straight, and the same is true with homo households. That is not the only result though. I live in the most well behaved white people magic land ever. I still know a bunch of guys who sell weed. That isn't the lifestyle that their home environment has tried to support, but certain influences have led them to that point.

I don't think sexuality is a choice, just like how I don't think I chose any of my other personality features. I think your environment dictates how you'll turn out. All these ideas that you've acquired over the years are because of your environment. You learned about that and so and so told you that, and you built an opinion about it. Your teacher mentioned that one thing and you took it as fact and began to live your life assuming that certain piece of information is true and with that in mind you acted differently than you would have otherwise if you had not acquired that information.

tl;dr lol gay