When a liberal looks at a black man he sees a man in a wheel chair struggling to reach the elevator buttons. When he looks at a white man, he sees an able bodied man who inconsiderately places buttons too high. The liberal feels a pang of guilt for his own able body and anguish over the plight of the handicapped man. The liberal chastises his fellow able bodied while attempting to push buttons for the handicapped.
This perverse view is racist because the liberal views himself as superior. For the liberal, those who would come to the aid of those weaker than themselves are inherently good and those who refuse are inherently bad and likely secretly desiring to take advantage of the unfortunate. Liberals believe you are racist because they know they are racist. However, they believe they are good racists who want to help the inferior and you are a bad racists because you want to hurt the inferior. Of course all of this is sick and twisted and completely consistent with nearly two generations of liberal thought.
Even if he were raised in a society free from liberal racism and still turned out to be a thug (bad apple syndrome), he would not have brazenly attacked Zimmerman. He would not have been conditioned by liberal racists to believe that he could audaciously attack a man without repurcussions.
The idea that race is some sort of title of nobility should have died with the Confederacy. But its pretty clear that Martin, and those who now award him sainthood, grew up believing it.