It's about modifying behaviour to make it acceptable to us. Nobody is debating that dogs shouldn't be shitting in the hall. But there are ways of modifying that behaviour.
Taking the "dominance" approach, you say for example "any dog who thinks that's easy pickings will learn they aren't". I am uncomfortable with this - what did you do to teach her not to take them? You did something to make her frightened so she wouldn't eat them - she is a dog, dogs have not got reason, they just have needs, the most powerful of which is food. Do not leave food lying around and expect a dumb (in the literal sense) animal to leave it alone. That's like standing in front of a charging elephant and expecting it to listen you you asking it to "please desist". They act on their natural instincts.
Taking the scientific approach you would see that a dog has a natural desire for food, so you would firstly stop increasing the dog's baseline anxiety by leaving food around and then inexplicably forbidding it to touch the food, and then start a programme of teaching the dog that by leaving the biscuits they can eventually gain a more desirable reward, such as a piece of chicken. But this takes ages and is boring so I don't leave my biscuits lying around.
Modify problem behaviours. Don't have unreasonably high expectations of an animal which has not got our powers of logic or reasoning. Don't abuse their good nature by misinterpreting their normal behaviours as naughty, dominant or wilful.