This is an interesting question and one that my friends and I used to talk about 25+ years ago. I am a metalhead and as such, I have always been labeled as a Satanist, but if it had not been for metal, I can tell you now, I would have ended up in prison or dead. It gave me an outlet for my serious anger issues. So with that in mind, how can it be bad, right? People look at things differently. Some people use dark humor to keep their sanity while others can't fathom and fear it. Same with music. If you are easily influenced, then you need to recognize that about yourself as stay away from music and really, any media, that might lead you down a dark path. The thing is, if you are one of those people, you do not get the right to tell others that what they choose is wrong. Why? Just because it was wrong for you, does not mean it is wrong for them. You are forcing your beliefs and prejudices on another then and that is wrong. That said, if you see someone is going down a dark path, then you can share your story with them and hope they can see it & the correlation with their current circumstances. Once again though, you can not force them, because 2 wrongs do not make a right. Really, the whole thing is about knowing who you are as a person and where you want to be. You have to acknowledge when something is not good for you, when something is good for you and when you just think/want something to be good for you because of your various personal reasons.