Kill him.

You bumrush him, landing a couple of weak punches and kicks.
He tries to fight back with his fragile frame and scholars arms, but ultimately he just curls up in a ball.
You tire yourself out, realizing you don't have the strength, anger, or weapon to kill a grown man, so you leave him be.
After a bit, he gets up and dusts himself off.

"Well, I cannot say I'm not offended by your sudden attack, but I certainly understand it.
I mean, you found yourself in an unfamiliar situation with an unfamiliar man, and you immediately took action to protect yourself.

niles reading a book

Niles is bruised, and cautious of you currently.
He's keeping his distance from you, and is preoccupying himself with meaningless reading.
You are both still trapped in this room together.