Given that this happened when you first started working, I was depressed to see that you have been on the forum even longer than I am, and at least at present reside in the part of the world from which I came (the Pacific North West), where I would have hoped that this attitude would have been slower to arise.
When I first started working, I believe that the blacks in my area were well-enough integrated (and few enough in number) that there never would have been any behaviour of this sort, nor would they have been cut slack for such idiotic things on account of race. My siblings (adopted from Asia) did encounter some discrimination from a small minority in the community, and I suspect that blacks might have as well, but it was a very rare awkward comment or action to which “Sticks and stones may break my bones” would suffice to respond. Not at the level of property destruction.
It was in Portland...
Its curious isn’t it...where did this attitude come from that is so prevalent today.