What a pillock.
I don't side with anyone who tries to talk about the danger to the race drivers. The corner workers know to wave a white flag in this situation. It means "slow vehicle on course ahead", and there is no "last lap" white flag, btw. It's not uncommon, and it could mean a disabled race car or an emergency vehicle. If I had been out there, I would have assumed it had a reason to be there and would have just gone around.
I'm not excusing his actions. He knew what he was doing when he did it. If he wanted to be funny, he failed, and if he wants to be "extreme", then get a real race car!