"Hip hop began in the 1970s. The art form, which originated in New York, provided Black and Latino youth with an outlet to express themselves, often speaking out about the poor conditions that exist within their communities. The development of the hip-hop culture created a movement that influenced the way we dress, speak and socialize. The emergence of "gangsta rap" in the 1980s marked the beginning of some disintegration of the positive images in hip-hop culture."

http://www.ehow.com/about_5418679_negative-rap-hip-hop-music.html