This letter in the Taipei Times says what I wanted to say, but doesn’t hold back any punches! But, then, it is easier for a Taiwanese to call other Taiwanese “racist.”
I believe that the attempt to exclude teachers from these countries has little to do with accents.
Rather, it has more to do with our narrow-minded calculation that these darker-skinned people (who would, presumably, be rather worse-off than most of us) don’t deserve the high salaries that the ministry proposes to pay. White native-speakers of English, on the other hand, are believed to be worth more than our own Taiwanese teachers.