What a Fake Slut!!

Yes, even though I just did a feminism post a couple days ago, here comes another one since I'm feeling particularly feminist-tastic and the last post was rather lack-luster anyhow, so hopefully this will make up for it :)
One of the biggest part of feminism, I think, is defending women's rights to live the sort of lifestyle they want. I don't mean that I think that everybody that wants one should get a Gucci bag or a nice house- I mean that EVERYBODY should be allowed to do what they want, so long as it's not hurting others and they're still working to get their fair pay and what not. When I say this, oftentimes most people agree with me.
"Of course people should be able to do what they want with their lives!" they often agree, "If I'm happier with a blue collar job on a construction site than I am in an office, who are they to judge?"
However, most people don't seem to realize this also extends to less socially acceptable lifestyles as well. That's why I get so upset whenever I hear otherwise open-minded people see a tanned skin, scantily clad girl walking around the beach and roll their eyes and say "What a fake slut."
Now, let's have a talk about those two words- "fake" and "slut."
For the average American at least, "fake" seems to mean those girls who get breast implants and tans and weaves and whatnot. Of course, usually when I defend a girl's right to be "fake" without getting any crap from other people, I'm usually specifically referring to more alternative fashions, but I feel that more "mainstream fake" like that is fine too, though others don't seem to. So, what's the problem here?
When I asked most people why they automatically hate these girls who are immaculately tan during the dead of winter, most of them replied with something along the lines of "Well, they're always so slutty and full of themselves!"
The ironic thing is, a lot of people saying this say they're against stereotyping at the same time. Well, what do they think this is? Whether you like it or not, it's stereotyping.
I admit- I used to be totally guilty of mentally judging "slutty" girls too. My wake up call came a while ago, when I was walking in the mall by myself. There was one girl who, while not dressed too suggestively, was dressed rather light for the middle of winter and had all the "fake" attributes I mentioned before- tanned skin, piercings, weaves, the whole shebang. I could see people glaring at her out of the corner of their eyes, shamelessly judging her. I'm ashamed to admit it now, but I was right there with them.
While everybody was so busy silently judging this girl, a little kid wandered by, clearly lost. Nobody stopped to help him, except this girl. She gently asked him where his mom was, and he said he didn't know. She left with him to help him find his mother, and though I don't know what happened after that as I was walking in an opposite direction at that point, I do know that what that girl did was nice and she didn't seem like the terrible,  obnoxious person I'd judged her to be.
This made me realize that no matter what, stereotyping is ridiculous and while it's perfectly human to judge somebody a little when you look at them it's best to try to keep an open mind.
However, when it comes to "sluts," nobody seems to be able to do that. Honestly, who are you to negatively judge a woman based on her sex life? If a woman doesn't want to have one partner and would rather sleep around, that's her choice, and I can never understand why people are so bothered by it. Unless she's sleeping with a married/taken man, nobody has any good reason to say bad things about her sex life, unless of course they have religious reservations (though I believe I've met five people who frequently "slut bash" that actually practice a religion at all- many are actually anti-religious, which I find very ironic and annoying).
So, I ask- why all the slut hate? Why does everybody feel it's okay to stereotype JUST with these girls, but nobody else? If you do stereotype now, just know it's a very foolish thing to do, and you're missing out on meeting lots of great people by doing this.