Good points. We won't know the truth until all facts are revealed.
This is a local interaction where the customers are living in the same neighborhood; how do we know for sure the previous customer isn't a friend of the two sisters who are now just denying knowing that customer? This restaurant might have jealousies from the locals who are trying to take it down, etc., and the paying sister was ready to bring her more talkative sister as a witness and power.
At the same time, the business owners should also be ready to suffer losses in their operations; they can't use another customer's non-payment to offset a paying customer, etc. It is always a challenge for businesses to offset losses and gains. This restaurant should just let the loss go and give the foods to one of these sisters; you can't take money and not give them the product they've paid for, just as you can't be forced to make the foods and then won't be paid for it or your work.
Our society needs to educate everyone more about how to respectfully interact with one another within diversity. We are living in diversity now.
It's just discrimination, but he's not racist. Afterall he did just serve some black folks before that incident. Now some other black folks are making a big deal about not getting served.
What's wrong is there is no compassion. As usually when someone is recording things to make a big deal. Most of the time, they're staging it already. Could this be such a scheme? Why don't they record the black person or group that did not pay and took off?