The bigger point is that in all probability, the client's costs were minor (<10k), and these kinds of bumps and scrapes that happen (and what one needs to budget for) when choosing to to push forward with a large-scale and obviously controversial project.
So discretion (and concern for the project's overall public image) would call for using a feather rather than a sledgehammer here, as I see it.
Your figure of "<10k" that you consider as "minor" shows that you have no idea how people get by. They were kind enough to explain in advance how they would proceed if the complainant pursued in their misguided attack, how more agreeable do you want them to be without similar complaints drowning them out?
So when I said "minor" not in comparison to his day job salary but as in, you know, the scheme of things.
You have no idea how people get by.
Gosh, it seems you know everything about me.