I go to Pride almost every year - mostly because it's a brilliant party and I like these kinds of festivals in general. I love the crazy fun and warm attitude and yes, even the spectacle of it all. My accountant dances on one of those floats in silver holographic briefs but in regular life, he's in a suit. It's just part of the fun. I don't go trying to understand what gay people are like because I know enough of them in my personal and professional life to know that they are just like straight people, except they prefer the same sex when it comes to dating and sex. It's no different than going to Mardi Gras and assuming that all women will flash their tits for a string of cheap plastic beads when really it's just part of the festival culture.
I don't think of gay men or lesbians in terms of stereotypes, although I *do* know some gay men that fit that stereotype by no fault of their own. They're not conforming to anything - they just like fashion and clubbing and having fun. I adore them! But I don't assume they are representative of the entire gay culture. Because this small segment is the most different from what guys and preconceived masculinity are assumed to be like, they probably just stand out more and that's how the stereotypes generate and gain momentum, thus totally negating the rest of the gay population because they're not as visible and just blend in with the rest of the crowd that forms what we see as typical examples of the 'male gender' or 'female gender'. If people live sheltered lives or live in areas where coming out is still not the norm, then they will probably look for the most obvious examples, which will always be stereotypes.
No matter which group you belong to (and I'm not just talking sexual orientation here), there is always going to be a stereotype. It's a thing that humans do. It could be for a sense of protecting oneself, it could be because of a lack of understanding, or it could just be outright stupidity. Nobody really knows why stereotypes exist, just that they do. There are myriad reasons.
Why?
There are gays who are out, and those that aren't. The ones that our out, tend to be VERY out. The ones that aren't, keep it to themselves. So just think about it. If you are walking down the street and see someone that is so flamboyant that everyone knows they are gay, the stereotype grows. They could have passed 10 gay guys, but if they act straight enough that no one knows they are gay, they don't fit the stereotype and it does nothing to destroy it.
Face it, everyone knows that not all gay people act a certain way. Everyone knows all black men don't have big cocks, or all Asian men have little ones. Everyone knows Jewish women don't all gossip. Everyone knows some old people drive well. Everyone knows some white men can jump and play basketball. Everyone knows all Texans don't ride horses to work or wear cowboy hats. It's generalities because enough of them do. It's how we group people, most likely because it's a protective measure. People who are most like us we feel safe around. People who are different from us we feel less so. Making those generalities helps us to set expectations when we meet someone new. For instance, you see a guy in a ski mask coming into the bank, are you going to think, "just because he's wearing a mask doesn't mean he's a thief, he could be going to a Halloween contest or going skiing," or are you going to dial 911?
As long as you understand that stereotypes are just that, and are willing to judge people for who they are, not on a stereotype, I don't see the harm.
I have a cousin(love him to death) who is the stereotype but I have friends you would never guess. I think we live in a narrow society that has to find a way to make sense of people who are unlike them. There are so many ways to live life and most mainstream people don't know that.