Why do people get p.o'ed about the KKK?

honestly I could careless I'm not a racist person but if racist want to start their own klan then let them I mean if I saw someone wearing a KKK outfit yeah I might think WTF but they are people too they just don't like other racist. If it happens in a temple or where ever it is held and it's behind closed doors and no one from other races are getting hurt or effected by it then why can't people just leave them alone? I would never join but if some one wants to join that's their life style and why should we all be mad over how someone chooses to have a certain life style?