That means “one doesn’t do that.”

As in insult politicians. Otherwise we’ll arrest you. “Speech raids” are a thing in Germany.
Germans are being arrested for insulting politicians — we need to protect free speech so it never happens here.
The First Amendment is our sacred safeguard against becoming a censorious hellscape — like Germany, where insulting a politician can land you in prison.
Even supposedly “free” Western countries are liable to crack down on free speech at a moment’s notice, as a recent “60 Minutes” segment makes clear.