President Donald Trump said Tuesday that the corporate chief executives who quit his advisory manufacturing council were "leaving out of embarrassment" for manufacturing products outside the U.S. Trump told reporters in the lobby of New York City's Trump Tower that the CEOs were not taking the issue of domestic production seriously. He said he had been lecturing them on what he said was the need to bring manufacturing back to the United States. Kenneth Frazier, the chief executive of Merck Pharmaceuticals, CEO Kevin Plank of the Under Armour sporting goods company and Brian Krzanich, who heads the technology giant Intel, have all quit Trump's American Manufacturing Council. They were joined Tuesday by a fourth corporate leader, Scott Paul of the Alliance for American Manufacturing. They apparently left the council to protest Trump's initial comments on Saturday's deadly racial violence in Charlottesville, Virginia, believing the president's early condemnation of racism to be weak. 'Grandstanders' Trump belittled the departures with a pointed retort on his Twitter account. "For every CEO that drops out of the Manufacturing Council, I have many to take their place. Grandstanders should not have gone on. JOBS!" he said. Doug McMillon, chief executive of Walmart, the world's largest retailer, joined the other executives in rebuking Trump on Tuesday. McMillon said Trump "missed a critical opportunity to help bring our country together by unequivocally rejecting the appalling actions of white supremacists." The Walmart chief added that Trump's Monday remarks explicitly condemning hate groups for the Charlottesville violence "were a step in the right direction, and we need that clarity and consistency in the future." Trump's initial remarks about the Charlottesville protest condemned the violence between white nationalists and counterprotesters, but did not single out neo-Nazis, the Ku Klux Klan and other hate groups by name. Instead, Trump said the unrest was caused by "many sides." He used the terms neo-Nazis, KKK and white supremacists when he made more explicit remarks two days later. He told reporters during the Trump Tower news conference that he wanted all the facts before making a detailed comment. One woman was killed during the white nationalists' protest of Charlottesville's planned removal of a statue of Confederate General Robert E. Lee. He commanded rebel forces in the U.S. Civil War of 1861-65, a war fought largely over slavery and states' rights. Heather Heyer was killed when a white nationalist demonstrator drove his car at high speed into a crowd of counterprotesters. Formerly a 'business genius' Merck chief Frazier was the first to quit the manufacturing council, saying Trump initially did not "clearly reject expressions of hatred, bigotry and group supremacy, which run counter to the American ideal that all people are created equal." Trump in July called Frazier a "business genius," but when he quit the manufacturing council, Trump, in less than a hour, said on Twitter that with Frazier leaving the panel, he would "have more time to LOWER RIPOFF DRUG PRICES!" Under Armour's Plank tweeted that he quit the council because he would rather unite people and promote diversity through the power of sports, not politics. Intel's Krzanich said he was resigning to highlight the "serious harm our divided political climate is causing to critical issues. I resigned because I want to make progress, while many in Washington seem more concerned with attacking anyone who disagrees with them. We should honor — not attack — those who have stood up for equality and other cherished American values." Paul, of the manufacturing lobbying group, said, "I'm resigning from the Manufacturing Jobs Initiative because it's the right thing for me to do."