RickN, as to messing with somebody's grave, I have walked on thousands of them (mowing), hoed weeds around tombstones, dug them, had a few fall in as I walked across them, and never once did anyone complain. My point is that there is nothing special about a grave except what those close to the occupant choose to invest in it. To publicly desecrate, even in a conceptual sense, a grave is of course offensive.
I'd disagree about there not being anything special about a grave. Mowing, etc is of course required. I still try to avoid walking across them when I visit cemeteries.
As to the OP, this is sick and should be offensive to any Christian, whether you agree with WBC or not.