If a policy is wrongheaded, feckless and corrupt, I take it personally and consider it a moral obligation to sound off and not shut up until it's fixed.
Sometimes I read a script and it's obvious from early on that it's one where the suspension of disbelief has to develop strongly from page one. Some are more reality-based.
Even if I would have left on a good note, there is still going to be people who don't like you, who don't like what you stand for. I can't worry about that.