The societal problem here is that antiSemitic tropes exist which are so widespread that people who are not antiSemitic can easily fall into using them.

If you focus on one of the PEOPLE who has used such a trope, and make the debate about whether or not they inadvertently or intentionally used the trope, then use of the trope in society will persist.

It's not about Rowling; and making it about Rowling insures the trope persists.