That's a well put original post.
I am a heterosexual male. Always have been, and I can't see how that wouldn't be the case for the rest of my life. I've had time to think that through on several occasions and I don't have any sexual feelings towards the same sex.
As for "Does sexuality matter?" in a more universal way: No. Except in some, not that usual, scenarios. To myself: Not really. Although I come from a very small place with a rather homophobic atmosphere (if you haven't lived that, you don't know), and I don't actually know any people in real life that I'd know to be gay or bi, or actually I do know a couple girls who are gay and bi, so I don't know any bisexual or gay males.
I'll admit that I won't feel completely comfortable if a gay guy is checking me out or hitting on me, but I'd say that's something I can't control. Although, when that happens, I'm polite about it and say I'm straight an not interested, if it isn't already clear.