If the perp had been a minority, we'd probably be seeing it replayed on TV incessantly and have rioting in the streets.
From my point of view the car backing up didn't pose any threat. However, the perp did pose a threat by trying to evade the cops for 90 minutes, driving the wrong direction, and driving thru a pedestrian walkway. As a result, he needed to be stopped. I don't know if excessive force was used, but I do know that the perp found out that crime doesn't pay.