I played a game once where the players decided that the King was evil and needed to be overthrown. The DM kept telling us that he was good. The peasants that we were trying to "free" kept telling us that the King was good and that they liked how things were going.
We didn't listen. We just ran around trying to take down "the man", burning whatever we could.
To the DM's credit, he didn't get pissed off, he just ran things normally. As in we were branded criminals, everyone hated us, normal villagers (the ones we were trying to "save") wanted us dead, etc.
It was great fun.