You don't politely ask your oppressors to give you the rights they have taken away from you.
It worked for King, it worked for Ghandi. Do you really think there could have been something like the civil rights laws -- born primarily of white people -- if the primary black person had been X and not King?
Yet it was Ghandi himself who, when asked if his peaceful tactics would have worked against Hitler, said, "probably not."
I'm not suggesting that white people are literally Hitler, but simply that there's a time and place for everything, including peace and violence. And I say that as someone who has never called for violence on anything ever.