Really is an interesting episode in a lot of ways, especially as societal conversations about racism shift -- caring less about intention and more about outcome.
Even so, it sure stretches my suspension of disbelief, to find it plausible that so many characters mispronounced "Tolkien Black's" name for 20+ seasons. Ignoring the L and pronouncing Tolkien as "Token" is almost as bad as pronouncing Sherlock's name as "Homes" instead of "Holmes," but people still know what you meant to say in the latter case.
Retconning is usually a dangerous game, and this episode makes me want to go back and see how many times Token's name appeared in written form (written by characters other than Cartman).