Playing games of this caliber, the extremely cerebral games, can often lead to very aggressive/childish behavior, I think. One chess master upon losing, famously declared, "I can't believe I have lost to this idiot!"
It is amazing, isn't it? I feel this way when I lose to Bob! There is such a feeling of superiority wrapped up with games of this kind. Some people only play games they win because of this! Others throw tantrums when they lose. It is surprising to see such a rule, but not totally unexpected. I can imagine there is quite a bit of hatred and snubbing that goes on at that level. And all of them likely feel superior to each other, and no one likes to be proved wrong about that!
Yes, enforcing manners is pretty sad, but the guy certainly knew about the rule. As for humiliation... yeah, it sort of goes along with what I was saying about superiority...