Because you're scared and she's not.

[ He's clearly agitated by talk of Lisa, but he tries. He frowns and he thinks and- ]

-what do you think she would do, if something she didn't understand tried to threaten her? And what do you think most humans would do? Or your father? Or you? Anyone else would attack it, or run away from it, or try to do what it wanted. She'd ask what it was and try to figure out how it worked and-

[ He actually shudders at that idea. ]