No surprise at all, for most of us who have been unfortunate enough to ever drive through a black area, we know that pigs are very clean animals compared with the average black.
There were no doubt trash cans all over the place, me I have a personal hate against litter, I would never throw a bottle on the ground I carry them around with me until I can throw them away proper, but to a black, they will shit all over their own front porch so they have no problem trashing any area they are at.

There must be lots of pics of the DC cleanup I found this one just browsing around, please post more if anyone finds some.