A lot of demons are. There are a few though, who border the line between what is considered Human and what is Demon.
Satan appears to be a really laid back King of Hell but in truth, he is very dark with manipulating people behind their backs. It's all how you perceive evil, too. We all have roles to play, even if we all don't agree with them.

Does Johnny think I'm evil? [He tries not to giggle]