I am happy to agree that modes are off-topic: Harker, as you say, mentions them only rarely.

My take on that is that Sharp's treatment of them was an example of cultural blindness - I wouldn't go as far as to call it racist, but at least it didn't occur to him that any music theory originating east of Vienna might be relevant to his project.

Harker looked only at much cruder examples of Sharp being narrowminded. But occasionally using racist language didn't have an adverse effect on what Sharp could discover, while not using the knowledge accumulated over millennia by "lesser breeds without the law" certainly did limit him.