I get your stance, I really do.
I guess the bottom line for me is that I think we should expect better from an NFL HC - whether it's his full-time job, or he's filling in. And I think Brady had every right to go tell him to eff off. I'm glad neither was penalized, because I think this kind of stuff probably happens in every game; just not so openly/obviously (because most HCs are smarter and more professional).
If a coach was doing what this clown was doing, and Josh Allen was on the other end of it, I'd be 100% in support of Josh telling the guy to go eff himself. And I still don't think it would get flagged. I hope not, anyway.
I guess I just think this could have been avoided if the coach wasn't being a dick.