If this isn't evidence of at least a kind of residual racism among a readership who is usually fairly intelligent, I don't know what is. Tyler Cowen posts at the Volokh Conspiracy (a high quality legal blog, for those who don't read it) that Mexican-Americans tend to lower the crime rate in cities where they have a high presence. From the very beginning of the comments, almost every comment tries to respond by changing the subject to illegal immigration, as if Mexican-Americans are somehow illegal immigrants. When did we ever pass any laws that prevented Mexicans from immigrating legally? How did they get to be Americans if they were illegal. Last I knew, the Bush plan hadn't been implemented, and that would take years before anyone who entered illegally could restore themselves to good faith to be considered for citizenship anyway.
This reveals something about the gut assumptions of the primarily libertarian and libertarian-grounded conservative audience of a high-powered intellectual blog (or at least about those most motivated to comment). American law-abiding citizens are being assumed to be criminals merely because they were born in Mexico. So Mexicans are apparently criminals just because of their country of origin, even if they're legal immigrants to this country. The only thing I can think of to explain that is some sort of racism, even if it's unintentional and unconscious. I've seen this phenomenon before, but it was particulary obvious, especially given the site it was taking place at. I don't think this is something inherent to libertarianism or to intellectualism, but I wonder if there is something attractive about libertarianism and libertarian-like conservatism among those who are really irrational about things like this.