It isn't "we're not gay" seating, it's "man spacing". It has nothing to do with sexuality, it has everything to do with a guy's gotta have his space. A hot chick can encroach, but that's because her presence overrides man spacing. A case of beer may also occupy the empty seat, because a case of beer overrides man spacing. But another guy encroaching on man spacing is just some guy in your space... He brings nothing of value into your space, unlike a hot chick or beer.
Get it?
Besides, you can bet that they guy walking around saying "I'm not gay" all the time is probably the gay guy anyhow. Not that there's anything wrong with that, but the ones making a big deal about it are the ones with the "problem".
I've been a fighter pilot for 15 years and I haven't ever seen another fighter pilot do anything to prove that he isn't gay, or feel any pressure to claim "not gay" status. The very few gay fighter pilots and WSOs I know didn't have anything to prove either, even though the AF didn't treat them very well.
Except for the F-15C drivers... They're all gay and desperate to prove they're not. But we all know the truth. Sinners.