Why is being nasty instead of being nice pay off

When I was in high school my best friend told me I was too nice and that people would like me if I wasn't so nice. I find this to be true some 30 years later. People just don't like it or YOU when you are nice to them.

Can someone please explain to me why:
#1 People generally like you better if you come off as a bitch
#2 You get more respect from people if you are nasty

I don't understand this and probably never will. I for one don't like being around people who constantly complain, are bitchy towards me and others without cause and are basically just plain nasty in their persona.

Can someone wise person explain this to me? If this is true how can I change and become bitchy so people will like me and respect me? How can I walk into a store and get the salesperson not to talk down to me? I get this constantly without justification and find it hard to fight back. Tweet