Not only are McGruder's comments moot, I would argue that they are perhaps hypocritical.
Over the years, McGruder's comic strip has come under fire for allegedly fostering racial stereotypes (the young black "gangsta" rapper, the angry black kid, the ditzy blonde, etc.). McGruder, of course, points out that this is not his intent.
However, if people are as ignorant and potentially racist as he argues here, then shouldn't he consider that such people COULD take the wrong message from his strip and that his strip COULD foster unfortunate ethnic stereotypes?
After all, there is precedent for that: Norman Lear created Archie Bunker to ridicule bigots, only to discover that some people were listening to Archie and going "yeah, that guy makes sense."
Couldn't the same thing happen with the "Boondocks" cast...especially if people are as McGruder claims?