96SS: OP was a normal passenger who became manifestly distraught upon returning to his seat. If I were his seatmate, this would be a situation I have never encountered, and I'd ask him if he wants to talk about it. Upon hearing his story I would ask if he wants police to meet our flight at our destination. If he says yes (which I'd advocate strongly), then I would pay for inflight wifi, which I have never done, to blast out (over private text messages and also in public on Facebook and Twitter), "I am in the air on UA flight XXX, seat XXX right now to Denver. A flight attendant is physically violent and behaving erratically onboard. Please call Denver airport police immediately and have them meet us at the gate."

Not to impugn anything about airport police, but they're generally not swamped with the type of stuff going on in the inner city. They will respond.