However, we always judge rap music, but we don't look at some of the rock music out there today.
I remember hearing rock songs that would talk about burning small animals and the devil and killing people. Suicide also seems to be one of the bigger topics in some of the rock I heard growing up. No one ever really says anything about that, but they turn right around talk about what black people listen to and do.
There's an entire subgenre of hip hop that talks about that stuff too. It's called horrorcore and people have been attacking that quite viciously for some time now. Granted most of those artists aren't my cup of tea because their lyrics typically don't talk about my style of horror, but yeah people are perhaps a bit too harsh on horrorcore artists when their lyrical content isn't all that different from those that thrash metal, black metal and death metal bands have been using for ages. It may not be my style, but some times I think the criticism is a bit too harsh.
Plus people have attacked that and all manner of rock through out history over lyrical content. They did it in the 60s with drug content, more of the same in 70s, but that's when people started thinking the devil was in every song. In the 80s they had the whole PMRC thing where it fever pitch and people flipped shit about Marilyn Manson and continue the satanic panic with regards to rock music. It was also during that time that everyone got up in arms about Cop Killer by rap metal band Body Count which is fronted by Gangsta Rap legend Ice T. However, Ice T had something to say when he and his band composed that song. It wasn't Cannibal Corpse who, no offense to their fans, wrote about seemingly mindless and ridiculously explicit gore with no intent other than to shock (which is precisely the reason I can't listen to them). But that's been going on for so long that it feels like you're beating a dead horse when someone says "OMG that rock band said something shocking!" People have been judging rock music since the 50s when a number of radio stations and older people were terrified of it because they thought it was too sexual and too black. That's right, back in the 50s, racism was a reason some people hated rock music. In fact, many of the early great pioneers were black Little Richard, Chuck Berry, Bo Diddley, Fats Domino, and many others were architects of the sound back then.
I can certainly tell you that the NSBM bands certainly aren't looked upon with kindness by most rock fans. I mean, nazi metal music seems kind of antithetical if you ask me. Especially considering what an inspiration the blues and jazz have been to metal musicians and all rock genres in general. It has always seemed absurd to be a racist and be a fan of rock music to me.
The other thing I think that upsets people with regards to this is the apparent degradation of a culture and music style that had revolutionary roots. The decay of a genre that was founded in social consciousness. Some people feel that it has been corrupted form it's original state. They're terrified that the revolutionary spirit from which hip hop first hip hop artists emerged has become lost in a sea of bling and braggadocio based rhymes. I have to admit that's one of the reasons I couldn't get into much rap music for a long time. That and the beats didn't seem quite as good for a long time.Even he first gangsta rappers were people with a revolutionary outlook. What people forget is that those artists were basically activists talking about unpleasant truths.
This is similar to one of the reasons a lot of people got up in arms about pop-punk bands in the punk subculture. It seemed so divorced from the rebellious, socially critical, often political nature of punk that most earlier forms had championed. People had a similar gripe about emo (which oddly enough did have revolutionary roots as protest against perceived lack of real emotion in mainstream music.) Grunge was sort of born of a similar reaction to Pop Metal/Glam Metal in the eighties.
However I won't argue that you don't have a good point. A lot of things that have origins in the culture of black people, music, fashion, slang, literature, and many other things have been ridiculed and treated as lesser if not out right ignored throughout history. We should be more careful and consider the reasons why we are criticizing something related to the culture of black people. Maybe we just don't understand as well as we think we do. No art should be considered totally above criticism, but we should be more mindful of why we're criticizing it.