Music and it's concept.?

Why is it that people judge other people by the music they listen to? Why is it the music people listen to effects the way they are? I love music, I only listen to rock,metal, and stuff like that. But I get judged all the time by the people who live around here. Sad to think from what music was to what it is now? It use to be blues, jazz, rock(Clical), and techno. Now they have so many varities and most of doesn't make since. For example, Rap, (Please don't take it as if I'm trying to put it down, It's just I find it quite annoying and moronic.) It makes most people illiterate and too y. And then theirs the stereotypical Rock which they have to be "Satanic worshippers"