Personally I don't know anyone who is truly evil, and if I did I would quickly disassociate myself from that person. The friends you keep and the people you spend time with help to shape others opinions of you, as well as how you view yourself.
There are many people out there that can be viewed as evil, and most often they suffer from some mental disorder. When we give them any attention, as you are doing now, their disorder worsens and they become "evil", as you call it.
If you really know someone who is evil, get that person some help. As has been said before, he or she likely does not know they are evil.