Your logic is wrong, pointing out his fallacies while you are even more in the wrong, and not even taking into account how rude you are arguing (because that's a rational behaviour to have).

Maybe an issue exists at an individual level, thus it may not be sufficient for claiming it is a social and generalized problem

I've never seen a Washington state license plate, but that doesn't mean it doesn't exist.

This is your fallacy, the debates isn't about if something exists but if something is a generalized problem to be solved. And such problems cannot be objectively defined as "a problem", it becomes a problem when enough people think and say it is.

I can find several other examples of people getting upset over cultural appropriation.

Yes but do these translate into a real problem?

the first article is about a mom mainly thinking about this concept and how it should apply. Nonetheless its importance is quite exaggerated