He understands what he did even if he knows he was enchanted when it happened. It was his actions that led to it but he was a little disappointed at Joker letting him do it. He's expecting something if not anything but such a sad face.

But she just deflates further into herself and he strokes her hair gently in return.

"It's because you're precious to him. I'm not. He's your big brother, is he not? That is what big brothers are suppose to do. They lie, cheat, and hide trying to protect those they love. I know I'd do just about anything for my family even if it meant smiling when I shouldn't."