Jeffrey Sonnenfeld, senior associate dean at the Yale School of Management, said Bill Ackman "last week kind of went off the edge" as the activist investor said he'd lost confidence in J.C. Penney's board.

"This is Bill Ackman engaging in basically frat boy-like temper tantrums," Sonnenfeld told Newsmax TV in an exclusive interview.

Ackman subsequently resigned from the board of the struggling department store operator, Thomson/Reuters reported this week.

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Ackman's Pershing Square Capital Management is Penney's biggest stockholder with a 17.7 percent stake. CNBC quoted Ackman as saying he had no immediate plans to sell.

Editor’s Note: Obama Donor Banned This Message (Shocking)

Ackman went public last week with statements saying he'd lost confidence in Penney's board and that Chairman Thomas Engibous should be replaced. Ackman and the board also were bickering over how quickly the company should replace CEO Mike Ullman.

"Even though he’s the largest shareholder, and yes, it’s a stake that’s ... perhaps 18 percent, that’s still not considered control, by the way, for a Delaware corporation," Sonnenfeld said.

"That would be crossing 40, 45 [percent]. But even so, it’s a big block and it’s the biggest block," he said.

"It still doesn’t give him the right to have destructive temper tantrums," he said.

"It’s pathological because, of course, it was creating uncertainty and distress both inside management, inside the employees and among the factors, the creditors out there, and not to mention customers," he said.

"The stock, of course, was taking a nosedive in the eyes of investors seeing this uncertainty."

Penney is trying to reacquire customers alienated by a reinvention plan put together by a former CEO backed by Ackman. Ron Johnson was ousted as CEO after 17 months because his changes caused sales declines, according to a Thomson/Reuters story.

Ackman joined the board in February 2011 and pushed the board to hire Johnson, who was described in the story as "a mastermind of Apple Inc.'s successful sores."

"Who is responsible for the genius of Apple stores?" asked Sonnenfeld. "It was not Ron Johnson. Ron Johnson was the guy who was going out to trade shows with self-congratulatory pitches and going on the media talking about it. But it was Steve Jobs who’s turning over the tables to take a look at where the seams were and what was being displayed. Ron Johnson, it was a wrong hire. Anybody could have made that mistake, perhaps, but the board, especially Bill Ackman, refused to learn it."

Johnson's plan called for the end of most discounts in favor of "every day" lower prices. He also wanted to split Penney into mini-shops devoted to brands or types of merchandise.

Ullman has worked to stabilize the business since returning to Penney in April by bringing back basic merchandise and more frequent sales eliminated by Johnson.

The story earlier in the week showed the company's stock has fallen nearly 38 percent since the beginning of the year and almost 70 percent since early last year when Johnson unveiled his transformation plan.

Editor’s Note: Obama Donor Banned This Message (Shocking)