What do you think of cheerleaders? middle and highschool?

I am a cheerleader for my middle school. and everyone always says ohhh shes a cheerleader slut! skank! etc. you know how it goes. why do people do that? its just a sport.. this may sound weird but im more tomboy then all girly.. and i hate the skirts! i just like to tumble and stunt. maybe you could help explain why? =) thanks.