Bill Clinton has a history of sometimes suffering from severe foot-in-mouth disease and veering dangerously off message while on the campaign trail for his wife, Hillary. On Thursday, a short video clip of the former president sparring with Black Lives Matter protesters from the stump in Philadelphia once again raised the question of whether Bill is actually helping or hurting Hillary's campaign.

The heated exchange began after the demonstrators interrupted Clinton several times while he was on stage, lambasting his administration's Violent Crime Control and Law Enforcement Act of 1994. The legislation has been blamed for ushering in an era of mass incarceration that disproportionately affects blacks and Latinos, raising the US prison population by more than a million.

But the part of the exchange that has been shared most widely on social media probably came when one of the protesters suggested Clinton should be charged with "crimes against humanity."

"I don't know how you would characterize the gang leaders who got 13-year-old kids hopped up on crack and sent them out on the street to murder other African-American children," Clinton said, pointing his finger at the crowd. "Maybe you thought they were good citizens."

"You are defending the people who killed the lives you say matter!" he went on. "Tell the truth. You are defending the people who caused young people to go out and take guns."

Clinton also defended the crime legislation, saying it helped bring about record lows in crime and murder rates.

"Because of that bill, we had a 25-year low in crime, a 33-year low in the murder rate — and listen to this — because of that and the background check law, a 46-year low in the deaths of people of gun violence," he said. "How do you think those lives were, that mattered? Whose lives were saved, that mattered?"

The Clinton campaign declined to comment Thursday, while the Sanders campaign did not immediately respond to an inquiry from VICE News.

Hillary Clinton and Sanders have openly attacked each other in recent days ahead of a crucial New York primary on April 19. Both candidates have also held rallies and town balls in largely black and Latino areas of New York this week, campaigning on a raft of issues including criminal justice reform and police brutality. Clinton's campaign, which has eagerly and successfully courted minority voters, has done so with the support from prominent black politicians, leaders, and relatives of black people who were killed by police.

The former secretary of state held an event in Brooklyn on Wednesday with a panel of prominent black women, including Chirlane McCray, the wife of New York Mayor Bill de Blasio, and Nicole Bell, the fiancée of Sean Bell, who was infamously shot by police 50 times on the night of their wedding in 2006.

"Nine years ago, I lost my fiancé, Sean Bell, in a police-involved shooting, and unfortunately, there are too many families with stories like mine," Bell said in a statement to the New York Times on Sunday. "[Hillary Clinton] understands that we need reforms that can be felt on our streets and in our communities," she added, declaring that she "will stand up to the gun lobby, work to end racial profiling, and make key investments to ensure that law enforcement officials have adequate training."

After several early episodes in which Hillary Clinton was heckled by Black Lives Matter protesters, she met with several activists from the movement and has since campaigned heavily on issues of criminal justice and ending excessive use of force by law enforcement. The Black Lives Matter movement, a nonpartisan coalition of groups and individual activists, has stated it will not endorse any one candidate in 2016.

Sanders has also sought to increase his support among black voters and remedy early criticisms that his campaign focused solely on economic insecurity, to the exclusion of race and other issues. Sanders has also experienced early run-ins with Black Lives Matter protesters at several campaign events. At one conference, demonstrators demanded that the senator recognize the names of black people who have died in police custody, including Sandra Bland, who was found handing in her Texas jail cell last July. Sanders received criticism for declining to "say her name" at the time, but later issued statements firmly stating that "black lives matter." He has since also campaigned heavily on the issue, often repeating the line, "When a police officer breaks the law, that officer must be held accountable," at rallies and events.

In February, Sanders received an endorsement from Erica Garner, the daughter of Eric Garner, who died in an illegal police chokehold in July 2014. On Wednesday, the senator elicited loud cheers at an event in Philadelphia when he said he would formally apologize for slavery if elected president.