Really hard question

My girlfriend told her mom she was seeing me (she's 17, I'm 20). Her mom disapproves im sure, but isnt stopping her, and asked the question of "what would a grown man want with a girl who needs to be home at 11"

First off, I think its a little unfair to ask me to justify my feelings for someone else just because of age. I understand where she is comming from as a mom, but as an adult since im SO grown up in her eyes, I also understand that its wrong to dislike someone before actually talking to them. Ive met her as I have been her waiter at the resturant i work at, but never talked to her about liking her daughter.

What do I do? What do I say? Do I run away? How do you answer a question like that? I mean I kind of wonder if I give her a response she doesnt expect if she'd think twice? Is she asking to prove there is no good reason? Im not in dire need of an answer YET, as I'll bullshit my way out, but I want a really good answer.

Jam it back in, in the dark.