I see your point, but he still knew cameras were focused on them the whole time, with no chance for her to say anything. And he must have known he blindsided her with the whole thing since they didn't know each other very well. Plus he set it up publicly as a crowd-pleaser, so I still don't get why he would be surprised she took up the "story" without being sincere.

To be fair he did realize later that he shouldn't have acted like he did over it, but even though I grew to like him later for a while I couldn't help wanting her to stay the heck away from him.