and what evil dreams would that be?
He already had what he wanted...He became the leader of the galaxy and to become that he had to eliminate the Jedi...He said himself that the Jedi could cause a civil war after what happened and he wanted peace...so they had to be killed if peace had to be kept
And civil war is exactly what happened but not by the Jedi but by the Rebellion...If Palpatine wanted to maintain the peace in the galaxy (from his point of view) he had to destroy them too.
I think many like the story that Palpatine is pure evil and he is really evil...but does he think of himself to be evil? Of course he had selfish evil plans in mind....but he thought that it was for a good cause...
I'm not saying he should join "Greenpeace" by now...but he indeed wanted peace, cause he said that in honesty to Anakin. He became honest about his plans after Mace was killed. The destruction of the Jedi...the destruction of the seperatists leaders, reaching peace.
Peace maybe wasn't his first priority...but if wanted to stay a leader he absolutely didn't want war anymore...cause that would only stand in his way to stay a leader.