Any CEO who stays on any of the White House business advisory councils will face backlash because they’ll be on the wrong side of history, Larry Summers told CNBC on Wednesday.

The former Clinton Treasury secretary and ex-Obama economic aide said on “Squawk on the Street” the controversy over President Donald Trump‘s comments regarding Saturday’s deadly white nationalist rally is “unlike anything we’ve seen before.”

Summers said there’s anyways room for debate on policy positions, “but this is traducing basic American traditions of justice, inclusion, and fairness.”

On Monday morning, Merck CEO Ken Frazier started the exodus from Trump’s manufacturing council. Less than 24-hours later, Intel CEO Brian Krzanich and Under Armour CEO Kevin Plank followed suit. On Tuesday, AFL-CIO President Richard Trumka, union colleague Thea Lee, and the president of the Alliance for American Manufacturing, Scott Paul, resigned as well.

“I cannot understand why others have not followed Ken Frazier out the door. I cannot understand why they have not endorsed his courageous action,” asked Summers, echoing his commentary which said all CEOs should quit Trump’s advisory councils. “This is not a happy day for American business.”

Summers also said Wednesday he’s surprised no officials of Trump’s administration have resigned.

“There’s a tradition in America of people of principle when they are sufficiently offended and disagree with their president on matters fundamental resign,” he said. “I have been disappointed that there have been no resignations on principle by the political appointees of this administration.”