Does it matter? You don't have the right to demand that everyone agree with you, even if you're right. We don't burn people at the stake or try to silence them for disagreement. Please stop trying to create unanimity; it's not healthy.

What we should punish people for: lying to Congress, taking or offering bribes, doing dishonest work while in the public employ. All of those apply, and any should be sufficient, at a bare minimum, to justify firing these professors. However, thinking that climate change doesn't exist or isn't anthropogenic is not a crime. Saying so is not a crime, either. And I'm damned glad of it!