Most educated coastal folks would not use "3 good reasons" in this case, but at least in my experience, in less educated communities in the South it is more likely to be phrased that way. I implicitly assumed that the teacher did not mean "good" pertaining to slavery, but that may be because I grew up in an environment with different colloquialisms than others. Frankly, if I were a sleep deprived teacher just trying to get something done, I could easily see myself making the same mistake and then seriously regretting that it warped my intention.

This is particularly interesting because I think that the use of language in this case actually reinforces the intent people read into the situation. With some people confused as to how this is "racist" because of a different reading of the language in addition to a different moral interpretation around the assignment.

But when I see good in quotations that usually means that it’s not actually good, but someone says it is. So I don’t know if the context is exactly “why does person x think it’s good” but it seems close and let’s you respond and think about something without actually agreeing it is truly good or the instructor recognizing it is good.

An example may be “describe how anchovies are ‘delicious’” although of course anchovies tasting horrible is in no way close to slavery. But might show how you ask the question by actually biasing that anchovies suck but you’re going to say they are delicious for the sake of thought.

If anything putting good in quotes signals that slavery is not good and biased the discussion. For most topics I think that will yield worse results, but slavery is fine to bias students against. I don’t really care if people keep open minds about slavery.