Wow. What a dum**ss. It must be a British thing, as Nigel Mansell once did something similar in a Grand Prix. I believe it was the British GP, and he had walked with the race. He decided to run the final lap slowly and wave to his cheering fans. Well he never made it to the line. I've heard two versions, one in which he let the revs drop to the car stalling, and another where he physically hit the 'kill' switch with his hand.
On a serious note, that was incredibly dangerous for not only that driver but the others around him including innocent bystanders. His actions were outrageous and I hope that his competition license was suspended. I'm not necessarily referring to the celebrating, but his actions after the fact. That speaks of an individual that cannot control himself and deserves some form of punishment in order to make a point. Hopefully he would then learn a lesson before he or someone else was hurt or worse. Motorsports are dangerous. That is why if you choose to participate it is your duty to minimize risk at all times. Otherwise you don't just threaten others, but the sport as a whole.
Ernest Hemingway is quoted as saying there are only 3 true sports: mountain climbing, bull fighting and auto racing. Everything else is just a game.