Using Rap and Poerty in the Classroom (3rd - 5th)

I recently taught an America's Choice (Literacy Program) lesson on "Writing for a purpose" to a 5th grade class. The lesson asked students to analyze written pieces and discuss what the purpose was behind the writing. I took the opportunity to use some of Tupac Shakur's poetry as the work we would analyze for “purpose” and “meaning”. We read "The Rose that Grew from Concrete" and "Sometimes I Cry". We also listened to the 3rd verse by Tupac in the song "Me against the World". I particularly wanted the students to hear this verse for the line where Tupac states, "The message I stress: Study your lessons. Don't settle for less. Even the genius asks questions." It was my thought students would respond to this coming from a Rapper more than if I tried to stress the importance of education as their teacher. The students written responses were very positive and a few students even wrote some rather impressive poetry about the struggles they face in life growing up in a city. I'm now trying to do more and more to use rap lyrics and poetry in the classroom when it comes to writing.
My reason and goal for this discussion is to find out what teachers think and what other teachers have done with rap in the classroom. What do educators think about using rap to help students gain interest in writing?
I personally love rap music because of the energy it contains and the impact it has on the listener. Unfortunately, in the case of negative rap music (rap that glorifies selling drugs, carrying guns, and disrespecting woman) it still has this energy and impact that is sometimes hard to erase from the memory. What can we do to promote positive rap music and celebrate hip/hop culture in the classroom? While still maintaining professionalism and not promoting children to listen to negative rap music?
Because to be honest I feel there is more hurtful rap music out there than helpful. Any thoughts or ideas? or even things you've tried in your classroom?