Also, don't hesitate to quote Pink Floyd and the Beatles as positive influences, eg. Can't Buy Me Love (teaches valuable lessons about wasting money on "love") or Hey Jude (super-duper motivational). On the Floyd side of the spectrum, you could talk about how The Wall shaped so many people to be what they are today, or you could say that Another Brick in the Wall is a huge negative influence if you want to score points with the teacher. I know Pink Floyd has changed my life for the better... and before you write me off as a hippie-stoner from the 50's, I'm 16. And I'll admit to hippie, but I'm not a stoner by any means.
On the other side of things, you could cite a lot of screamo/emo stuff as negative influences, but I don't know any of those bands so I can't make suggestions. You could, jokingly if you're out of ideas, cite MJ's Beat It as responsible for household violence, but then again, you could cite some of his other songs as very positive influences. Pretty much all of rap that's about bitch's and ho's can be said to be negative, but again, I can't make specific suggestions as I don't listen to rap.
You could blame Sublime and Bob Marley and all sorts of ska/reggae music for getting people into drugs, but then you could also attribute some very positive aspects of life to those genres, such as an ever-present happiness, joy, and general optimism conveyed by much of Bob Marley's music. Quote specifically, Three Little Birds. Amazing song, and a very positive vibe and message to it.
On the topic of accusing movies etc. for negative influences, you could take a line or two from the family guy theme song and apply it indirectly to your paper. It shouldn't be hard to find examples to fit the bill of the lines I'm thinking of:
"It seems to me, that all you see,
is violence in movies, and sex on tv..."
You could easily claim that violent movies lead to violent kids... Here's a page with some excellent facts and it is linked to reliable sources:
http://http://www.mediafamily.org/facts/facts_vlent.shi
There are some pretty decisive results if you google "movie violence effect on kids statistics", the above link being one of the first links if you make the search.
Overall, I think I've given you some pretty good ideas... I hope this all helps. Now I've got to get back to my own homework.
Good luck.