The paying diner and his friend will eventually walk out of the resturant and the resturant will eventually close. Then the uninvited and unpaying diners will start to get hungry and angry. The first person they’ll blame is the greedy resturant owner who was driven to bankruptcy and then they’ll turn on the former paying diner.
In the end the freeloaders will turn on each other because that’s all that will be left.
The “paying diners” should understand that they need to own and practice with firearms in the face of the eventuality of the freeloaders personally coming to take whatever he has left.