Therefore, when your 4 year old eats your 5 year old's cookie, it isn't productive to demand that the 4 year be held to account for "how it would make YOU feel if HE ate YOUR cookie". It's confusing and irrelevant to the child.
Since parents for most of the last century have used exactly those words on little kids, I have illustrated a disagreement between me and a hypothetical parent, and resolved it with a very, very basic finding of developmental psychology.
That disagreement is not very relevant to whatever it is our disagreement is, but it does illustrate that the logic you're deploying isn't... um... controlling? here.
Incidentally, isn't it a little bit weird that I'm taking this side of a discussion against the author of the "Don't Fight" iPhone application? =)