Pretty sure there is some philosophical belief that states that an individual exist only moment to moment and is essentially a different person in each of those moments, or some crap like that. Which would make labeling in all forms pretty invalid.
But if a dude willingly sucks another dude's wang, that's gay. You can't suck some dude's wang and be straight, it just doesn't work. And if you're not straight, you've got to be something else...right? So at the very least, these guys were at one moment in time gay or bi. So they're just defining themselves by their past in this situation, something people due all the time.
I think your real beef is with attention whores (Or maybe labels in general), not with someone's sexual preferences. I think almost everyone dislikes them.