Do the unaware racists watch shows like Girls, which is pretty much the most racist thing that's ever been filmed? Everyone knows that in real life 20-something hip white girls in Manhattan have friends of lot of different races! To not the depict the one Asian friend they hung out with every couple of weeks is pretty horrendous.
In all seriousness, I do agree with the concept of unaware racism, but I think pretty much everyone has it. Some people just have it more than others.
Also the argument that racism can't be involved because Zimmerman is Latino is kind of dumb. The only way that argument might make sense is if you accept the definition of racism as something that can only come from a group with power, like white people. I don't, because that's not a sensible definition, but rather one constructed to make it easier to make a certain kind of political argument so that people can't complain about "reverse racism." While I don't think reverse racism is a major epidemic threatening American society, saying "only whites can be racist" is either such a gross oversimplification or etymological trickery. But the truth is, we don't need to believe that only whites can be racist for us to condemn racism. Racism isn't more morally depending on who it's coming from, although it can have more severe effects.