Suppose you go to a restaurant and you order a meal, when it arrives it tastes terrible and looks even worse, should you pay for it?

I send it back and give them a chance to fix it ... If it's unacceptable the second time, I talk to the manager and tell them what's wrong. 

Usually, the manager will either give me a chance to order another item without charge for the first ... Or even offer the other item for free ... Or comp the meals of everyone at the table ... Or a combination of those.

But if all else failed ... No, I would not pay for an inedible meal.  If they want to call the police - I'd be happy to wait around and have the officers taste the food.  ;)

I politely say, this doesn't look good. I'll order something else. I never eat food that doesn't look good.

If you eat it .. Hell yes you should pay for it.

It is not ok to eat an entire meal or any portion beyond tasting it then refuse to pay for it.  If you eat it there is a level of assumed acceptance .. And you are expected to pay for something you have accepted on those terms.

If however, you taste it and you refuse it because you find something wrong with it (other than personal preference) .. then, you should not be expected to pay for it.

For example if you order a stew and it has carrots in it .. of which you are either allergic to or simply don't like carrots, that is not a good reason to not pay for your meal.  Just because it has carrots in it does not deem it to have something 'wrong' with it.  If there was evidence that meal was spoiled, or mouldy or has hair in it  or it's not cooked as ordered .. THEN there is 'something' wrong with it.

I say if you eat it you pay for it, but if it's bad from begining, and refuse to eat it, then I won't pay for it.

Most good restaurants know they are selling a dining "experience" of which the food is admittedly a major part, but still only a part.

And a menu is considered an "implied contract" legally.

So my take when I enter a restaurant is that I expect the "experience" to fall within the acceptable range---and I am nothing if not a reasonable man.

So if something goes wrong, depending on what I think needs to be done to bring my dining experience back on track, I may just start over (for example, if my wait was much longer than it should have been, I just "begin again" when I get to my table) or I decide whether the waiter or waitress can best handle the issue or whether I should go directly to the manager.

Probably has only happened about 5-10 times over many years, but I've always obtained a satisfactory resolution for the problem.

First thing you do is tell your waiter or waitress that you wish to see the Manager. Then take it up to him/her and tell them what's going on. Give them a chance to make it right and if that doesn't work, just tell them you're not paying for it. Not much they can really do about it. A good Manager will bend over backwards to please his customers.

I know a few people that have worked in the restaurant business in their younger years, one is now a federal judge and the another is a psychiatrist. They have all told me to never send a meal back to get "fixed", the chef takes great offense and you never know what extras will garnish your entree. At that point, advise the manager, pay for what you've already eaten and had to drink and leave. Get something to eat elsewhere.

Kitchen mistakes happen.  Things burn, etc.  It's better for the restaurant if you tell them there was a problem with your food and let them fix or give you something else than if you pay, walk out and tell all your friends how bad the food is.