TRUE Satanists, ie, members of the Church of Satan, are typically okay. Their "Ten Commandments" actually involve not killing and raping people. However, the band Mayhem aren't what you would call "true" Satanists, since if I remember correctly there is only one remaining original member. All the others either killed each other or are in jail for killing each other... And in really horrible ways too.
There are Nazi-esque bands, but none that are known outside of racist/Nazi-esque circles. I don't think.
Basically, what people need to remember is that music has however much power as you give it. The fact that people commit violent crimes shouldn't be blamed on music%u2014it should be blamed on the fact that there are dipshits out there who misinterpret it, or think it's a bright idea to do what song lyrics say...