Stupidity: When the saw yo-yo comes down for the third time, Bond grabs the cord to pull the wielder down off the gallery. That was, when you think about it, a patently bad idea. If the yo-yo hadn't become stuck in the desk, Bond would be collecting his fingers in his hat (note that the blades are still spinning as Bond grabs). (01:15:45)
Stupidity: Khan's backgammon games make no sense by conventional rules. He claims to have won the first game even though he has a counter on the bar. His opponent is well behind but since he hasn't borne off any pieces he should have continued to avoid losing a gammon and having to pay double stakes. In the second game Khan rolls a double six but he doesn't bear off before Bond takes his turn. (00:29:30)
Chosen answer: The satisfaction of knowing he'll win, the thrill of pulling one over on someone; maybe like Goldfinger, he just doesn't like to lose under any circumstances.
Captain Defenestrator