content: I'm going to play devil's advocate here (in no way do I support the guy lol):  Not sure that means you should slam into her as fast as possible though.  I guess he wanted to teach her a lesson ie. you scratch my back I'll scratch yours.  She made him feel what it's like to have someone abruptly stop you from having fun.  He wanted payback ie. "this is what happens when you brake and someone is speeding behind you".  Watching how her neck snapped back  I suppose he didn't expect that to happen (neither did I lol).  His 'payback' was more than what he bargained for, which is what makes the video funny/shocking. You can hear him sounding concerned near the end. He definitely had a bad day that day.