Mike, they used you as a pawn. Why were you chosen probably will never be known. It sounds like if not you, another white person would have been chosen to cover their ass. Most likely, they did it because they had poor documentation on the black employees tardiness, they let several white employees "slide" on tardiness (on purpose or accident), or they were simply fearful of an uproar.

"Jim, we gotta fire this Bill guy today. Well, Rob, before you do, document a white guy fast so they can't say we haven't written up/fired any white employees. Well, that Mike guy missed a day last week, he is smart and will understand what we are doing."