The guy who got clipped was brake checking the SUV. But why? They don't usually outright harass people. They're dicks, but usually just end up fucking themselves up.
And I think from when the video starts, the SUV made the right move. It's not a good idea to run over people chasing you, unless you enjoy prolonged litigation. Best bet is to find a police station (NYC, most likely not carrying), but somewhere it states he had his tires slashed at the original altercation.