Food doesn't fly from the pantry into the child's mouth however children can only eat what their parents buy them. There are minor deviations from this rule e.g. the child has money to buy something nutritious or they can source food from another household. Otherwise having junk food in the house pretty much guarantees it'll find its way into the child's stomach.

You're comparing apples to oranges.

For the sake of the exercise I can compare apples to oranges. The exercise is to identify fundamental flaws in the OP's reasoning, not make simple analogies. The OP wants to ban passive smoking in the most private of spaces - feel free to explain how you do that in a way that won't be worse than exposing a child to passive smoking.