If fact, the debat is not over. Is man the cause? We don't know. If a politician like Al Gore makes a speech saying he knows all about the situation, I accept that behavior. It's what politicians do. But that man is being aided by a lot of scientists, and they seem to have contempt for people who doubt their pet theory.
Personally, I think we are in a time period where science has become more politicized than it ought to be.
Yes, there are some scientists who behave this way. In general, seems like with global warming there's been a perverse feedback: certain politicians seized upon the science because they think its ramifications fits their ideology; scientists in return enjoy the attention and authority the politicians bestow upon them, and (in many cases) inflate the certitude of their predictions.