Rafael Mangual on the negative was unusually haughty for a debate. Several times he didn't use his entire time. And he declined to ask his opponent (Balko) any questions. Mangual came off as extremely confident and Balko came off as increasing bewildered and resorted to dark comments about Mangual being dishonest. Balko ultimately won (+20% to +10%). Towards the end Mangual definitely said things that sounded bad, like jailing parents didn't lead to bad outcomes for children to the extent that the jailed parent was a bad influence anyways. Overall, the question framing seemed rough for Mangual because its easy to change the topic from police brutality, to jury selection, to over-incarceration. Though I guess that can just mean that Balko is more correct. Mangual came off as much smarter here than in his writing.
The philosophical aspect of the debate was what it meant to by "systemically racist." Balko claimed that because the criminal justice system was designed in the Jim Crow era it had racism embedded in it and so even if individual cops weren't racist it was designed to have racist outcomes. His prime example was small towns in Missouri were designed to avoid segregation and used cops to extract revenue from blacks.
Mangual refused to cede ground philosophically here, claiming that a system can't be racist without racists. And if the participants were making decisions to reduce crime they can't be considered racist even if the system was counter-productively harsh. He noted that the majority of the congressional black caucus supported the crime bill. And that even low estimates of the impact of police claim that they caused 20-25% of the reduction in crime since the 90s.
The empirical part of the argument was also very heated. Balko opened with claiming that 25:1 studies show that the criminal justice system is racist (including one that shows disproportionate traffic stops of black people goes down at night). Mangual claimed that once you control for differences in crime rates (which he considered homicides not drug use to be the right proxy) the racial differences went away.
In general, Mangual came off as more knowledgeable for each individual issue. For instance, with stop-and-frisk Mangual claimed that racial differences in finding guns was because each individual officer had a quota even in white neighborhoods where the frisk would return little. And that once you use micro-neighborhood data the impact was statisitcally significant.
The debate quickly devolved into Balko claiming that Manhattan Institute types cherry-picking the one "man bites dog" story not finding racial differences. And Mangual claiming that he already skimmed Balko's list of 25 studies and found them all to not have the proper controls (which Balko was sarcastic about him being able to read that fast).
Balko's list is here https://www.washingtonpost.com/graphics/2020/opinions/systemic-racism-police-evidence-criminal-justice-system/