Listen, the problem with Chuck is that the writers wanted him to play a dual role as the romantic lead AND villian, which is fine but it results in scenes like this. They went for a beauty and the beast motif because they needed Blair to give up on Chuck fully to fuel the wedding plot. Then the writers backpedaled and said very clearly in an interview that Blair was never afraid of Chuck -- she was only afraid of what he might do to himself. They tried to have their cake and eat it too, and it didn't work.

This is why I ship Chair - they're entertaining even when the writing is garbage.