This example of dialect discrimination surprised me and made me wonder how extensive dialect discrimination is within English language learning. I've been subjected to dialect discrimination in my own learning, with Canadian French, Mexican and Puerto Rican Spanish, and Bavarian German all being looked down upon by my native speaker teachers, but, as a native English speaker with my English instruction all within the United States, do not know anything about English dialect discrimination in a learning setting.
So, my questions are: how common has dialect discrimination been in your English language learning? Where was your instructor from and what dialect did s/he discriminate against? Was a reason given for the discrimination?