Personally I don't see it as evil (save for the Snake Man thing). I think it's more of a way (in his mind) to bring order in the various incarnations that you mentioned. Either he did it as a way bring an end to the war and KEEP it finished by taking over and making all sorts of laws, or he took over Skeletor's position to sort of bring order to the Dark Hemisphere. Either way it's more of a fall to the wayside rather than "Oh he's evil now! Ooooo!" It's a way of making things a little more grey rather than black or white.