Well, almost 70 years ago, that German dictator made his ideology law, and what did the people in Germany do(no offense to German people, it's just how all humans are)? Protest? No, they just let it all happen because it wasn't a disadvantage to them. However, sometime later, there was an actress who went nude for a film, and then suddenly everyone said she was a shame to the German people.
What I want to say is that (Imperial) people don't care if others have to die as long they're alive and well themselves.
However, there were some people who disliked him (not necessarily for his ideology, also because eventually he started being less careful for civilian deaths, etc), but they didn't protest because they were not so dumb to start protesting to be eventually executed.
I can't believe every Imperial citizen agreed with the emperor that they HAD to take revenge at the Republic and the Jedi, there must have been some who just wanted to live in peace and leave the Republic for what it is, but if they would have started to protest, they would have all just been killed.