That would be pretty damning to the driver if the rumor is true, but you don't try to force the dude to stop. You have his plates and you can tail him. It is not the biker's job to carry out justice.
Not really. If you watch all those videos and see how this mob was riding through traffic, it'd be pretty hard to blame anyone driving a car for colliding with one of them.
Here's the RR driver's wife and kid who were in the car with him.
Here's how the RR driver ended up when they finally got him out of the truck.