A state where black men are incarcerated at twice the rate of the national average served as the backdrop for Thursday night's PBS Democratic debate in Milwaukee -- and the important question of criminal justice reform.

This is one of the great tragedies in our country today. We can no longer sweep it under the rug. It has to be dealt with, Sen. Bernie Sanders (I-Vt.) said.

After noting that 1 out of every 4 black children will end up in prison and calling for an end to over-policing in black communities, Sanders said seeing videos of black people killed by police is exhausting.

I think we can all agree that we are sick and tired of seeing videos on the television of unarmed African-Americans shot and killed, he said adding that any police officer who breaks the law will be held accountable.