So to recap... all I said was that something appears to be missing from the story and it seems you agree. IronMaus actually goes on to say "The escort had only heard about the bad check guy. He hadn't seen his varying info sporadically posted online. He didn't know what I knew." which is where it gets a little fuzzy trying to justify the assault. And frankly- there is no justification.
End the session. Ask for cash. Offer to escort the client to an ATM in the hotel, or find another method of payment. Insist the client leave their ID behind until the cash is given. Loads of other choices rather than bash somebody's face in. Literally- do not normalize violence based on non-payment or perceived scam.