The problem is, they are the mouth piece. The majority of blacks agree with them to some degree or another.
I know this story is upsetting to you, Stevio, but you're throwing out a generality that just isn't true. The majority of blacks have never sided with the Black Panthers, or with any other violent black organization.
As with any racial or social group, there will always be some number who agree with nutjobs like the NBPP, but they are decidedly in the minority.