"Just because hes an Emperor doesnt make him such a bad guy or a bad poltical system or even make him a bad ruler. Empires have worked in the past, and the most successful civilization ever the Roman Empire was ruled by Emperors" one of the principals of civilization is that the leader follow the will of the people. yes in episode 3 the people willing give up their power to allow a dictatorship. BUT...by the time of episode 4, palpatine no longer has the backing of the people. they want him, and his dictatorship gone. the fact that he will do anything to hold on to his power, resist the will of the people, and even go so far as killing them in masse, makes him evil.