I have to agree on all counts. I don't think it was intended as a slam against non-whites...actually, I think it was the opposite, but it does not take much imagination to see how this could cause offense. Since there is already a decent contingent on the web that thinks of mmm readers as a bunch of upper-middle class white men, this is probably not a good thing.
Again, I don't think it was meant to offend, but it most certainly will. And yes, mmm can do as he likes, and I'll still read everything he writes, but if I were in his shoes I'd toss it.