A CBS 60 Minutes report interviewed billionaires taking The Giving Pledge, a promise to give away at least half of their wealth while alive or in their will. 60 Minutes applauded billionaire Pete Peterson, but Sen. Bernie Sanders questions the nature of Peterson's so-called philanthropy.

"I am not quite sure why 60 Minutes calls Wall Street billionaire Pete Peterson a philanthropist," Sanders wrote to 60 Minutes. "You said his cause is cutting the national debt. Does he want his wealthy friends and large corporations to pay higher tax rates to reduce the deficit? No. Does he support a tax on Wall Street speculators who caused the worst financial crisis since the Great Depression?  No.  What Pete Peterson has done is throw hundreds of millions of dollars into lobbying campaigns to cut Social Security, Medicare and disabled veterans’ benefits. That, to my mind, is not philanthropy." 

Watch the 60 Minutes report here and watch Sen. Sanders' response here.