That was clearly meant to be a joke. Black guys not trusting the cops, knowing what it means to be chased by the police even though you're innocent.

This may be my attempting to understand Hollywood writers, but with the guy's skin colour and age, I got the impression that maybe he'd been arrested for a crime he didn't commit, and saw in Reacher someone like himself.
But again, I'm playing mind-games with executive writers I haven't met, so I'm only guessing based on trends I've seen in other movies.