The point is that it's too easy for a malicious actor to utilize this kind of thing to keep the "wrong" people from participating in politics.

I am sure the OP's suggestion was in good faith, just that they weren't aware of some of the history and potential repercussions.

Maybe you're misunderstand, and if not I think your response is a bit disingenuous given that the commenter is saying the test can be used to marginalize a minority.

The commenter's point is that these "tests" can be designed to be difficult for one race/community, but easy for another, thus preventing them from holding an office.

Nope. Imagine a 99% white town where a Black man wants to run for mayor. Sorry pal, you failed the literacy test.