It's no surprise when hack pundits like Michelle Malkin do it--but it certainly is when Judge Posner and Professors Bradley and Goldsmith pick up and effectively legitimize the same misinformation.
UPDATE: In the comments at the second link, above, Professor Bradley (Duke) comments:
I can’t speak to Judge Posner’s views, but certainly Jack Goldsmith and I were not trying to make any revisionist argument about Korematsu or the internment policy in the casebook note referred to above. Indeed, we try not to be argumentative at all in the casebook. Our goal there was merely to give students a sense of the mindset of some people at the time (e.g., in the discredited DeWitt report) and then ask questions about how we should think about that mindset. It looks like the first sentence of that note in particular is responsible for the misimpression, so we will be sure to tone it down in the next edition of the casebook, and also probably cite to some better materials.