I think this is one reason live play is so much different than online and also why tourneys are so different than cash games. Obviously this pro thought he was behind - whether set or overpair (just because he asked him about a set doesn't mean that's really what he believes the guy has). Online you're going with stats, patterns and math. Live, he's getting a read off this guy, and he's going to trust it.
The other part - tourneys. While he could say "screw it" and make the guy pay in a cash game - having to reload if he's wrong, in a tourney you rarely can afford to be wrong.
I'm not saying his play was correct. I'm not saying I would've done the same. All I'm saying is it doesn't sound crazy that he laid it down.