I almost got into a similar fight a few years back in a Chinese takeaway. An exceedingly unpleasant man terrorised the young teenagers taking orders, and of course, their customer service programming kicked in, despite their visible horror at his utterly unreasonable behaviour. Whilst waiting for my order, the abuse got worse and worse (the bloke's order had been delayed due to a kitchen mix-up over one of the dishes, which was hardly the fault of the teenagers at the counter). Eventually listening to this became intolerable, so I placed myself between the man and the teenagers, and told him, in no uncertain terms, that if he didn't stop yelling and swearing at them, I would call the police. He then started some pre-fight argy-bargy shoving, but his food arrived before he could get too violent.

The takeaway gave me a discount to say thank you, which frankly is what you deserved for your actions.