Professor Obama is looking to grade you on your car-buying preferences. Beginning with the 2012 model year, new vehicles will carry revised window stickers bearing ratings from "A+" to "D," with the highest marks reserved for choices the administration endorses and the lowest for those it frowns upon. This is just the latest example of the nanny state mentality that has taken hold inside the Beltway. The schoolmarms at the Environmental Protection Agency and Department of Transportation jointly proposed the new labels Monday. The idea is to give government-subsidized electric vehicles -