If the bloke thought that was funny, how far was he willing to go? Bomb hoax for example? Maybe the crew thought that by sorting him out now they may get a message through to him, preventing something a bit more serious in the future. It could also be that if the other pax, who do smoke, saw him 'smoking' and the crew aren't doing anything about it, they'd all light up as well. Then the crew would have a hell of a time trying to explain why its ok for him and not for them....Just my thoughts.
Cheers.