Its harder -- or, perhaps more accurately, "less of an apparently viable course of action" -- if you have experience, first- or second-hand, which indicates that failure to submit to even superficially non-mandatory requests of a police officer has a non-negligible likelihood of resulting in escalation with potentially serious personal consequences.

I suspect that part of eevilspock's basis for the statement was a belief (which I would think is justified) that these experiences are substantially correlated with race.