The joke is that he does know. She lies and he's aware of it, even if he won't point it out right now. It doesn't matter how many times she takes him out, it doesn't matter what she does to him, he'd never turn her away. For better or worse, he'll be by her side.

When she kisses him again he's quick to return it, the way he leans into the contact needy and passionate. He wants her to be demanding, he wants her to be pushy and greedy. That's how he feels, after all, teeth finding their way to her lower lip once more. He's not made of glass, after all, and as such doesn't want her treating him like he is.

He's not human.