Did you notice the video was edited between when the driver tried to escape out the passenger side and the cop started hitting him AND the news station's graphics covered up where the cop's fist was actually landing? Gee, nothing to see there.
I've been hit with plenty of stuff litterbugs toss out the window when I'm riding my bike behind them, usually lit cigarette butts.
AFAIK, you cannot ever legally throw anything out of a moving car, well maybe a newspaper if you're a paper boy. But these guys were begging for police attention and they got it. Everyone knows the cops can legally order people out of a vehicle. That usually starts the process for a Terry Frisk and these thugs gave the cops all the reason they needed. Again, I suffer from white privilege, but I always, always have one or more guns with me when I get pulled over and somehow they don't even ask me for my permit or disarm me for the duration of the stop. But then I don't throw stuff out my window, mouth off or try to run. Call me crazy.