there's no real correlation between crossdressing and sexual preference anyway. hard as it may to believe, a man doesn't have to pretend to be a woman to love another man. 'gender confusion' is a whole other issue and even then, it's actually perfectly normal for a child at a young age to explore various things (the perennial example of the little boy trying on mommy's heels for example). but all that is really beyond the scope of this thread i think.
gay days (and there are two separate groups who compete and have their own functions -
http://www.gaydays.com and
http://www.gayday.com) is not a disney sanctioned function, but neither is MouseFest or ArielCon and many other functions that go on throughout the year.
the crowd impact really is minimal. it's a slow time at Disney anyway. You do see a disproportionate amount of red and presumably like-gendered couples (although from my experience, there are many groups of people rather than couples per se). Not much different on the surface than when Mommy hangs out with her best friend or Daddy hangs out with his. There is a lot of hand holding and other obvious closeness (lots of heads on shoulders on the bus for example), but there's typically no disrespectful behavior. Disney wouldn't allow it from any couple, gay or straight. Not to say it doesn't happen, but it's not as blatant as one might really expect (or perhaps hope).
Bottom line, Disney is still a family destination and most people tend to respect that. And many of the gay couples who participate in Gay Days at WDW have children of their own.
And beyond all that, it can't go unnoticed that Disney isn't exactly a good place to avoid gay people altogether any day of the year.
All that aside, I happened to be in MK for a period of time this previous year due to a tour and checking out other things. It didn't seem particularly crowded to me at all, but the red shirts are definitely noticeable. I took this shot mid-morning from the train station:
i'm pretty sure you won't see anyone dressed or behaving inappropriately in it, but I didn't study it all that hard either.