Mayor Pete Buttigieg angrily slapped down a man who heckled him at a campaign stop in Iowa saying black people should 'stop committing crimes and doing drugs.'

The 2020 presidential hopeful was interrupted during a speech at an Independence Day campaign stop in Carroll County, Iowa on Thursday.

Footage shows him responding to the heckler: 'Sir, I think that racism is not going to help us get out of this.'

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Buttigieg condemned a member of the crowd who interrupted his speech saying black people should 'stop committing crimes and doing drugs.'

Man booed at Pete Buttigieg event after racist comment.



"Racism is not going to help us get out of this," Buttigieg tells him, to applause. "Racism has no place in American politics or in American law enforcement. Next question." https://t.co/NkJuIoh4fP pic.twitter.com/iBt6pwnr2H — ABC News (@ABC) July 4, 2019

Boos ring out as the man claimed his comment had 'nothing to do with race' but Buttigieg and later called for an investigation of the incident.

'The fact that a black person is four times as likely as a white person to be incarcerated for the exact same crime is evidence of systemic racism,' Buttigieg added.

'It is evidence if systemic racism, and with all due respect, sir, racism makes it harder for good police officers to do their job too. It is a smear on law enforcement.'

The 37-year-old South Bend mayor has struggled with racial issues in past weeks after the fatal shooting of a African American man by a cop in his hometown.

Buttigieg was in Chicago to address Rev. Jesse Jackson's Rainbow PUSH Coalition International Convention Business Breakfast.

He used the speech as an opportunity to address racial issues in the country and tout his Douglass Plan - named after abolitionist Frederick Douglass - to increase economic prosperity in black communities.

But first he admitted he is struggling to gain votes in the African-American community, a strong bloc of Democratic voters, particularly in big cities like Chicago, Philadelphia and Miami - cities that could play crucial roles in the 2020 presidential election.

South Bend Mayor Pete Buttigieg speaks at the Carroll County Democrats Fourth of July Barbecue where the incident took place

'There's a lot of voters I need to get to know and who need to get to know me. They need to understand the details of the Douglass plan that we're continuing to roll out.

'And, frankly, they need to see me in action for a longer period of time,' Buttigieg told reporters before he addressed Jackson's event.

'Look when you're new on the scene and you're not from a community of color, you've got to work much harder in order to earn that trust because trust is largely a function of quantity time. I'm committed to doing that work.

'But, even more, the most important question is - will our policy benefit Black Americans and all Americans. And if that happens and, if I can show that, I think the politics will start to take care of themselves,' he added.

Buttigieg was responding to a question about a new CNN poll that showed him with 0 per cent of support from black voters nationally. Joe Biden did the best among that voting bloc, followed by Kamala Harris.