“A man's grammar, like Caesar's wife, should not only be pure, but above suspicion of impurity.” said Poe.

Now that might be true with a Jock from Glasgow who has a strong accent but not true of Ivan from Russia or Ubuntu from Africa. The thing is this Jock can leave most of his accent outside the classroom but Ivan can't bring any above suspicion grammar into the classroom. Am I right or am I right?

Native speakers can speak how they like so any comparisons between some of them and non-native speakers is erroneous.