How is this defensible? Asserting that by virtue of their powerlessness black people can't be racist? That's a statement that should offend anyone, especially black people.

Racism, sexism, etc. are characterized by the desire to damage a certain group while propping up another by making broad-scoped and baseless inferiority/superiority statements, often followed up by aggressive actions. It's not necessary for one group to be "in power" for this to happen. Racism in cases where minorities are the perpetrators is exactly as unacceptable as in any other circumstance and people who defend that should be called out for it.

In short, and conveniently looping back to the actual topic at hand: behaving like an asshole is never OK.

The difference between racism (an institutionalized system wherein a majority race discriminates against minority races) and racism (an arbitrary action that reveals a preference of one race over another) is a constant source of confusion in these discussions. The former definition is used most often in academia; the latter definition is much more common in casual conversation.

When one person says "black people can't be racist" and another person says "black people can indeed be racist," they are using the word two different ways and meaning two different things. It has derailed more threads than I care to remember.

Is there a good source for your first definition? I've never come across this distinction so directly before, and the line between the two is still a little blurry. I hate to get all [citation needed] on you, but it just seems to me that the 'institutionalized system' is nothing more than the vast repetition of many 'arbitrary actions'. Is there a simple textbook example contrasting the two?

Take a look at the sociological definition of racism on the Wikipedia article: http://en.wikipedia.org/wiki/Racism#Sociological

Hey thanks, that's definitely helpful. I wanted to read the Cazenave paper (paywall), but 'centrality' led me to a Google Book [1] which briefly explains MMRI (salience, centrality, regard, ideology). Understanding the differences between these basically answers my question.

1: Culture, Motivation, and Learning: A Multicultural Perspective edited by Farideh Salili, Rumjahn Hoosain, p. 327-328

I would say you are confusing 'defensible' - a reasonable, sane person could hold this view with the concept of 'I agree with this'. I happen not to agree with it but I could have a reasonable exchange of views with someone who did.