this is probably one of those things that can't really be explained over a message board, but to chime in w/stelfox & ripley; it's not about any reluctance, stemming from political correctness or guilt or what have you, to call people who aren't white "racist". it's just incorrect to apply the term in that manner. racism has to do not only with power, but with power structures & institutions. so even grievous individual cases, like a white person being mugged in a black neighborhood w/presumable racial overtones, don't transcend those overarching forces. nobody is defending Theo Parrish or hypothetical muggers, nor is anyone claiming that racial prejudice of any kind is good or desirable.
the difference, is between prejudice & racism. all racism stems includes prejudice, but "racism" by definition implies systematic power, and it flows in one direction in relation to power. white people don't have a monopoly on racism by any means, but they control the most wealth/territory/resources & have done so for a long time, so generally they have gained/gain the most benefit from the status quo. the same thing goes for male/straight/wealthy/etc - for each one of those pieces you get an inherent advantage, & well it might not ensure success it does, as stelfox pointed out, make the idea of gay heterophobia or female sexism against men an absurd one.
to further confuse the matter of power, in situations where dominance is less clear, more fluid, it's harder to differentiate; I'm thinking about parts of the Balkans, the tangled web of relationships between Israel/Palestinians/other Arabs, the complex rivalries between different immigrant groups in the U.S., and so on as always w/race things quickly get very fucking complicated if you delve into any situation in any depth, even if in this case w/Parrish things are pretty clear-cut.
like I said, a message board doesn't really do this justice. plus, it's kind of semantics at this point, with "racism" and the oxymoron "reverse-racism" getting tossed around so much that the former is almost redefined by the contexts people use it in. it's like Chapelle - tons & tons of people laughed at the racial humor while totally missing the point.