So... because some people do it, it's OK? What a great argument... If an instructor gives you poor marks because of a difference of opinion, you can and should appeal to the academic provost (or principal, I suppose, in High School). If your essay was well reasoned and supported by facts, there was no reason to just take the grade. That kind of behavior is completely unacceptable, whether it comes from the left or the right.
The analogy of grade redistribution to progressive taxation may or may not be apt, I don't care to argue either way. But calling it Obamanization is misleading: I don't see McCain calling for a flat tax, ergo McCain supports similar socialist policies, ergo McCain is a socialist. Call it McCaininating instead, or just call it socialist, but that would totally defeat the purpose, wouldn't it.