This isn't the progression in my experience. Or in any example I've ever heard of. I've dealt with a fair few physically violent people in my time. Race never came into it. I've been called "ni**er" a few times, it never made me angry, and the people who used it shrank rather than grew bolder when I laughed at them.

Don't get me wrong, if I'm surrounded by a group of klansmen shouting the n-word at me, I'll be fearful for my safety. But the potential violence is the issue, not the word. They could be calling me "sweetheart" and I'd be just as worried.

p.s I remember that NPR story too!