Anakin thought they were evil because they separated him from his mother and left her to die in slavery, ignored his visions of the future, tried to commit a coup against a democratically elected official and attempted to use extrajudicial force to execute said official, didn't let him pursue love, blocked him from accessing educational materials relating to the dark side that he wanted because he was both hunting a sith lord and trying to learn about his visions said sith lord implanted in him after the Jedi wouldn't take him seriously about it and finally, he was sick and tired of fighting in a war for his entire adult life that he felt could've ended long ago if not for the jedi's incompetence and when it came down to directing an Inquisition or letting your kids who are about to be born grow up in a time of war just like you did he said fuck it and proceeded to actually solve all those problems overnight but did it evil style.