It was the first thing that CNN viewers heard as the news conference ended, an assessment both acidic and incisive, the sort of judgment not usually uttered by Very Important Television Anchors.

“You have been watching,” said the disembodied voice of Anderson Cooper, “one of the most disgraceful performances by an American president at a summit in front of a Russian leader that I’ve ever seen.”

Perhaps Mr. Cooper had briefly forgotten the mores of his profession — stolidity and a Cronkite-ian cool — in the heat of a surreal live event: a public pas de deux on Monday between President Trump and President Vladimir V. Putin of Russia, in which the president criticized United States intelligence agencies and declined multiple opportunities to blame Mr. Putin for interfering in American elections.

But Mr. Cooper’s remark, though pointed, was not far removed from the nonplused reactions of his fellow network stars, who seemed to channel a level of genuine shock rare even in the chaotic Trump era.