If accurate, this is despicable and hopefully we will find the criminal and lock him up for a long, long time. Scum like this belongs in hell.
If this is a staged event, a crime never really happened, anybody involved with knowingly spreading this is going straight to hell when they die.
Personally, I find the story suspect. For one, who the heck is capable of carving a "B" with an assault knife on somebody's cheek? Secondly, why would a petty street criminal care about presidential politics when most of the time they only care about their next hit of whatever drug they're hooked on at the moment? Finally, why would he look at a car's bumper when his primary objective is to commit the robbery and get away with it? I would imagine a criminal would be far more likely to be looking around for witnesses/cops, a clean getaway, than keeping an eye on his victim's car bumper...
I don't want to believe that this woman is making up the story, but it just seems a little too perfect for the McCain campaign, especially since the McCain campaign just announced that they were going all into Pennsylvania, and nothing would terrify older whites more than this. And as you noted, some other things about the just story seem odd.