Are you trying to say that I meant ignorance of hip-hop music and culture is the origin of "nasty" subjects in the music? If so, no. Hip-hop is not all "positive" in the first place.
I don't see 2Pac as completely negative. He makes "nasty" music, and also music with consciousness and meaning. That's admirable and very human. No one is perfect.
People get pleasure from music because they either can relate to it, or it's something they aspire to relate to. Music, as with other forms of entertainment (video games, movies, etc.), don't cause you to perform an action or become violent. They just illustrate feelings that are already present within us.
Not all music is "positive." Topics of drugs, promiscuity, and violence are not only present in hip-hop, but also in rock. It's hypocritical to say that hip-hop is negative for containing these topics.
Furthermore, music with a "negative" subject, can either glorify bad behavior, or inform and educate people about what is wrong with society. In the latter, the music is not negative, it's realistic.
Now, "gangsta" rap. I'm obligated to talk about it, since it's the most frequently mentioned sub-genre to describe the whole culture. I like to say that there are two forms of it. The original one - honest, aggressive, and offensive albeit with good intentions, and the corrupted one - with no positive messages.
Early gangsta rap had much political and social commentary in it. (Of course with profanity and violence in between.) Over time the positive messages grew less, and the sub-genre was simplified to just drugs, violence, and promiscuity. If you listen to modern commercial hip-hop, this is, unfortunately, most of what you will hear.
TLDR: Hip-hop is not more or less negative than any other genre.