Driver has anger management problem. Was affronted that car was parked too close behind (necessary to ensure rear of medium-sized saloon did not overhang parking bay). Vehicles not touching. GL07 LOU occupied front parking bay so able to drive off in a forward direction unhindered. Touchy that car behind was 'too' close and turned into an abusive child. Presumably BMWs require other cars to maintain social distancing, in much the same way as most of us do when it comes to their owners.