Why is rap(black) criticized for its violent, drug, ual, ist, misogynist content yet heavy metal(white)?

.....constantly gets excused and/or ignored for its equally violent content. Metal music speaks a lot about drugs, cide and suicide yet society much rather bash and har the rappers. I'm not dissing metal, I love Korn, Slipknot, Ozzy, Marilyn and a few others but at the end of the day, why is it okay for "white people music" to say certain things but "black people music" gets blames for many of the problems we have in today's society?