The audience at Tuesday’s democratic debate in South Carolina booed Vermont Senator Bernie Sanders for criticizing former Vice President Joe Biden‘s voting history on trade and the Iraq War.

In his defense for giving gun manufacturers a pass throughout his voting record as senator, Sanders fought back by saying, “Joe has voted for terrible trade agreements.”

He later went on to continue defending his actions, saying that his voting record on guns were “bad votes,” and that he now has a D- rating by the National Rifle Association. He also credited former New York City mayor Mike Bloomberg for his “aggressive” action against gun violence. 

“The American people now understand that we must be aggressive on gun safety, not be dictated to by the NRA and I am proud that I have a D-minus rating from the NRA. If elected, it will get worse than that,” he said.