What measure is an accent?

So, this is a bit old, took me a long time to get to it, but in addition to they're ridiculous immigration law, Arizona has also been evaluating English teachers by their accents.  Language Log has a pretty good article about it.  For me it basically boils down to this:  These teachers already have certification of their English fluency, and English is very wide-ranging in terms of differing dialects and native accents, including having several different standards for different countries that a certain amount of foreign accent isn't that far from the norm.  Not only that, the same teachers being targeted because of foreign accents may speak the native language of the ESL students they teach, which can benefit their learning.  They shouldn't be discriminated against because they have not 100% internalized the phonology of some native variety of English.