First, did the original comments include the comma? I don't know, I haven't really been able to find where the original comments came from.
Second, I doubt a similar "inner-city, uneducated" comment would draw the same defense.
Third, the New York Times actually made the argument for the non-comma version.
Lastly, the less educated a voter was in the previous two elections, the more likely they were to vote for Obama (except for post-graduate). So perhaps it changes with the situation. Link