Overt racism is like a formal declaration of war whereas passive or ingrained racism is like fighting the War on Terror. Overt racism has a face and can be attributed to that one person's or small group's upbringing and life experience. It's something you can lash out at and break the teeth of, or report to the police or the community at large. Passive racism has no face. You can try to fight it, but if no one else sees it then suddenly you're crazy, or overly sensitive, or making mountains out of molehills. For me, one clear example is the difference in the way people of color are treated if they speak with an accent vs. how white people are treated if they speak with an accent. On some level, it's a psychological trigger that lets the listener know that the speaker is not from wherever "here" is. The almost automatic assumption for most people would be that the white with an accent must be intelligent, because they speak more than one language. The automatic assumption for the person of color is that they don't speak English correctly.
In America, white people with an accent - unless it's a few very specific hillbilly or redneck accents - come from somewhere likely to be more civilized than where you are. Accentless English is best found in NorCal and the Pacific Northwest, places that were hinterlands until the 1950s. Even a Philly accent speaks of a culture more refined than yours. Sweden? Ireland? France? Forget about it. In America, non-white poeple with an accent are upstarts and foreigners from somewhere less civilized. It doesn't matter if Dr. Singh attended Harvard medical school; we're going to hearken back to Apu on the Simpsons because frankly, negative stereotypes are all we know. The accent matters more than you'd think. I've worked with black producers from the UK and everyone treats them as Brits, not as blacks. A South Indian with a British accent will encounter a great deal less racism than a South Indian with an Indian accent. Gilmore Girls featured a black gay man with a French "gay" accent for seasons; to the best of my knowledge, "race" never figured into the show but "gay" and "french" did. While acknowledging that this is a conscious choice made by a team creating fiction, I think it's also important to note that they were following norms.
Points well taken. Out of curiosity, have you read Thinking, Fast and Slow by Daniel Kahneman? I just started reading it and I don't know that it deals with racism at all, but it is very interesting to read what this guy has to say about human behavior and how the mind works. It reminds me a bit of Dan Ariely's Predictably Irrational, which I'm pretty sure we've talked about in the past.