The fact that there are racial biases in what prosecutors offer between black and white is misleading at best. It simply follows from the facts that we already have: blacks are convicted more often. If blacks are convicted more often, they have longer rap sheets on average. You are unlikely to get a better plea deal if you have a history of committing crime.

Now, if they had gone and showed that first time offenders, for example, had shown a racial bias between blacks and whites, you'd have me impressed.

In effect, you are going back to the original argument, that it's just systemic racism. Unfortunately, you have not provided any falsifiable evidence that this is true.