Unfortunately, many guests try to cheat the hosts in this way. And Airbnb can do nothing about it, if the guests are not willing to pay (and there is no deposit, that covers such situations).
What any host can do without help from AirBnb support:
1) Never allow unpaid guests enter your home until the payment issue is resolved. Of course, the number of people, who paid their stay, can enter.
2) Send money request to the guests through AirBnb and wait until it is accepted. Don't forget to mention in AirBnb messages the concept of the money request.
3) If the guests are aggressive, call the police.
Of course, you should report the problem to Airbnb anyway, just in case.