There is a popular argument that roughly goes like this: Mexico mistreats immigrants, so its president should not lecture us even if Arizona mistreat immigrants. Felipe Calderón was also asked about it.
Andres Oppenheimer has a good column looking at how although Mexico has (as anyone who studies immigration knows) human right problems with regard to Central American immigrants, its laws are not like Arizona's. But I particularly agree with this:
Mexico's mistreatment of Central American migrants should be no excuse for laws like Arizona's. And the Arizona law's abuses should be no excuse for Mexico's failure to crack down on its police forces for human rights abuses against undocumented immigrants. Both are wrong, and both should be denounced.