If the people complaining about what he said were saying something like "we are offended by the implication that all people of Mexican descent are illegals" or "we are offended at the implication that all illegals are Mexican" or even "we think that Mr. Nagin needs to choose his words more wisely because people can take offense at things not intended to be offensive" then you might have a point, but I think it's obvious that he wasn't complaining about the ethnic heritage of the people in NO.

The fact of the matter is that a Mexican is a citizen of Mexico. Mr. Nagin may certainly have been using it in a multitude of different ways. I'm not intending to outlaw metaphor. But no one seems to consider the notion that he might have been using the word's denotative meaning. And my problem with that is that if we can't use the word "Mexican" to mean "Mexican", our language is shrinking and not growing.