Sacred Haven of Debauchery

why do people love negativity and aggression so much?

Because it's fun. What could be more entertaining than reading an article about a maniac while sipping tea? And aggressive music is very dynamic, and that's what makes it good. Also, heavy metal is great for relaxing.

Added 1 minute ago
And what do we even mean by "evil songs"? Does Voltaire have evil songs? (Judging by the title of one of them, yes)