Yes, but you're not quibbling about the title. Because the title doesn't say anything about the status of the slave trade at all. You're quibbling about this line:

"There’s one more sign of progress that our friend would notice; there’s no more slave trade."

I suspect you, as two other people did, saw "slave trade" and unintentionally read "slavery". Especially as your initial objection was "claiming that slavery is no longer an issue is one of [the times you're wrong]." As you say, wording matters, and this wasn't even close to my wording.

Given that the article is about racism and our hypothetical man is from the 1800s, I think it's extremely obvious what I was referring to. Thousands of people have read the article, and I only two other people have made this mistake.

As you say, I have a good track record of making corrections where they're called for. I have no problem admitting where I'm wrong or imprecise. But this just feels like nitpicking. You're welcome to disagree of course.