Stereotypes exist because they are true, whether people want to accept it or not. Even by trying to deny a stereotype and not conform to it you enter another one, not meant to offend anyone, this is the basis of things like sociology though in an academic sense they try and mince words more.
The thing is that when your dealing with large groups like "gays", "lesbians", or the ethnic group of your choice, there are enough people where there are differant cliques and stereotypes, some of which are larger/more common than others.
It's like with gays you have the flaming "Fabulous" crowd, those that act just like girls, hyper-macho types, and of course the ultra aggressive leather clad "bull fruits", just to name a few. There is no single stereotype. What's more differant groups do not nessicarly get along even within a group that might have general, political solidarity. With gay men for example a lot do not care for the whole "flaming" schtick that you most often see in the media, and can be fairly brutal to people who are that way.
When it comes to Lesbians you of course have the whole "bull" stereotype which are the really aggressive ones. Ones who act like guys. Ultra feminist types, and of course arty types who are really into the beauty of the female form, etc... who are pretty much the equivilent of the ultra-macho gay bodybuilder.
So while you can say that with Lesbians, the whole "one acts as a man, one acts as a woman" is a relatively common stereotype, it is not *the* stereotype because there isn't one. Like any LARGE group if you say "all people of this type generally conform to this stereotype" youd be wrong, though it's been proven on many occasions pretty much everyone conforms to some stereotype, even if they do so by trying to rebell against the most well known stereotypes and then wind up doing the same exact thing as everyone else who is rebelling and thus form a new stereotype.
As disturbing as it is for people who like to think each individual is a unique flower differant from all others, we're actually pretty predictable, our social instincts wire us that way.
One of the most lulzworthy things about people, is that one common advertising techniques is to imply that a certain product or service will allow someone to "break the mould" and "pull away from the pack" and be more unique and individual, because that is what everyone wants. Yet the thing is that since everyone wants it (hence the mass appeal) it is also a predictable human stereotype, and part of the same mentality that is allegedly being broken away from.
Apologies to those this might offend, but these are my thoughts. It also has nothing to do with homosexuals (though I'm responding to that example), but everyone.
It also doesn't pick on only minorities. With the WASP Male "majority" in the US consider that stereotypes include like the urban, oblivious, mostly self-centered, yet pretentiously liberal yuppie used for laughs in shows like "Seinfeld", and of course "Rednecks" to name two of the ones most singled out and made fun of. Then of course you've got things like the repressed intellectual white-collar "office drone" and that entire sub-culture, and the blue-collar stereotype of the low-IQ, "beer drinking man" with simple tastes and priorities.
