While this is bad, base on histroy I've read, this is tamed. There are so many screwed up history event in our own world, one piece looks like a day at bootcamp. You can't say Oda isn't doing a good job at making us dislike the CD. I would say, their appearance and actions are not frequent enough to complain. Remember how the narrator dug it into our heads how much the people of wano were suffering under kaido? That is a frequency I consider annoying to the point of desensitizing the audience.