It's a complicated issue, but black poverty and white poverty aren't the same. Sure there are lots of poor white people in the country. For instance, they weren't systematically trapped in ghettos like black people. They didn't have their neighborhoods flooded with drugs like black people. If you look back, violence sharply increased in the black community with the advent of the War on Drugs and the introduction of crack. I think what we're seeing in the black community is more akin to what was seen in Italian communities during prohibition than to random poor white neighborhoods.
Anyway, the answer to your question is likely more complicated than I'm making it. I'm pretty sure the increased violence has resulted from a variety of factors.
