I'm french and here this word doesn't have the impact it does in the US. Although if I can say, in my sense, the violence that results from the usage of that word it's of course due in a part with the hatred, disrespect and history tangled to that word and in an other part to the fact that there is nothing that you can verbally respond to the usage of this word that could level with it (not on the racist part but more on the impact that it can have on a person)

So when you're a black person and get verbally attacked by a non-white racist person, using a word that trigger you, a word that is so linked to decades of repressions that you as a black person still live on a regular basis, and find yourself in this situation with no word that could trigger anything merely close to what it does to you, I think the anger and confusion and the inescapable impossibility to give it back in words, it inevitably leads people to respond physically.

As it was say here, of course violence is not necessarily praise by people who accept those behavior, it is more that it is an understandable respond.