Wouldn't the level of discrimination be directly proportional to the views of the individual? I love to listen to my clients who hail from Zimbabwe. English is their native language, though their pronunciation is markedly different from my own. To a lesser degree I appreciate the gentle lilt of Trinidadians. My least favourite is a heavy Jamaican accent, until I have become accustomed to it, because I have to try harder to understand. All of us share English as our native language. I don't agree that ?'murricans "are less willing to engage in mutual give and take," though if students complaining is the measure for your comment, I guess I understand.
As for what method is best, isn't this too subjective?
I've made scores of ESL referrals over the years and note the feedback I received from my clients most resembles Craven's comments. Same language tutoring was helpful in the beginning stages, but once the rudiments were mastered, motivated students believed they needed the challenge of ?'English only' instruction to improve. I found that result counterintuitive, but there you have it.