I want to cancel my orders !! angrily !!

Why is it when it comes to food and hunger, people gets angry so easily ?
I know you're hungry, but we're doing the best we can here.
If you want fast food then go to a fast food restaurant, and then what ? you're gonna get angry because there's a long line there too ?

So a family came and ordered stuff and a fish dish that requires some time to cook.
20 minutes later, 2 guy came and complained that their orders haven't arrived yet, but other guests have had their orders.
We asked the kitchen and they're still preparing it and we explained that the other guests might have their orders first because their orders take 2 seconds to prepare and it was a different dish.
5 minutes later, the whole family came to us at the cashier, angrily and the dad said "I want to cancel my orders, I'll pay for what's there on the table and I want to take away the chicken dish"
our waiter then handled the chicken dish and put it in a doggy bag for them to take away.
So we decided that they didn't have to pay for anything because it's partly our fault, but hey... in my defense, he ordered that fish dish that takes a long time to cook, not our fault.
All the drinks were there, the chicken dish and the rice was there, but the fish and something else wasn't there yet.
So I said "The meal's free sir, we're very sorry for the inconvenience"
and they didn't even say anything, they just left
but before they left, they give us the "I want to kill you" look
the look was so hateful, it was unbelievable
It's scary how people can get that angry and hateful over food.
I know you're hungry, so eat what's on the table first, and if it's a full house on the restaurant, you can't expect to get your food in 5 minutes !!
You should see his face, it was pure hatred
People scare me sometimes, just because they pay for a meal doesn't make them God