why is a [censored] such a bad thing?

[gamblore99]

I accidentally accused a friend of being a [censored] today and she went nuts (I told her someone said she gives a lot of blowjobs). Anyways, as the conversation progressed she told me she was really upset that I thought she was a skanky slu.t, especially since we are good friends.

And this is where the reason for this post comes up. So what if a girl gets around? Sex is a natural and healthy thing and I don't see why people should think any less of a girl who sleeps around.
I used to think very differently, and was very anti-[censored]. But now I have matured more, and don't see anything really wrong with it.