i think think of sexuality kind of like i think of hand dominance. vast majority are right handed (straight) a few are ambidextrous (bi) and some are left (gay/lesbian). being anything but right handed is probably harder (left handed scissors? gmafb). also, i never recall choosing to be right handed and i never remember choosing to be attracted to females so i think you're just predisposed one way or the other.
i also think that anyone who runs around caring about something as insignificant as what hand someone chooses to write with is weird just like i think someone who cares about whether some guy wants to make out with another guy is weird. like, you're the rough ridin' weirdo in the situation bro. running around caring deeply about things like what hand someone wants to throw a ball with and whether or not some woman wants to grab the boobs of another woman vs the balls of some guy or whatever. just such a weird thing to care so much about i guess.
