Are some people so awful as to be unworthy of any friendship?

Dennis Rodman is friends with North Korean dictator, Kim Jong Un. When asked about it, "Rodman said he hoped the friendly competition would "open the doors" to "talk about certain things," but he isn't going to bring up the regime's human rights abuses. "I am not going to sit there and go 'Hey guy, you are doing the wrong thing. That is not the right way to do it. He is my friend first... and I love him," Rodman told reporters at Beijing airport. Is Rodman's approach wrong? Are some people so bad that they aren't worthy of any friendship? If so, when? Being a murderous tyrant seems to be a clear-cut case, but what about more common failings in a person?