A civil discussion with a small child

This morning I was having a discussion with one of my children about the wisdom and consequences of future actions. The way the conversation evolved cracked me up.
YHN: “No, you can’t put the horsie in the bathtub, because it has batteries.”
Child: “Yes, I can.”
YHN: “No, see it will get wet and eventually corroded and ruined.”
Child: “No, it won’t.”
YHN: “Yes, it will. Whatever gives you the idea that you can put this horsie in the bathtub?”
Child: “[Elder Sibling] said it was okay.”
Right. This would be the [Elder Sibling] who Child opposes at just about every turn, particularly when it comes to [Elder Sibling] informing Child what Child may or may not do. With toys, generally.
Our conversation ran aimlessly for a good while after that with Child sticking firmly to the assertion that throwing a horsie in the bathtub was okay under the aegis of [Elder Sibling]’s authoritative permission*. The discussion was more or less amicable and The Man did not have to break out the tools of repression. I.e., Child was eventually distracted by something shiny.
Deploying a cherry-picked authority in support of what you already believe or want to do, to avoid engaging evidence and rationale (and yes, opposing authority) which you fear might contradict your pre-existing position or desire is apparently an early-formed trait.
No wonder we have such difficulty maturing past it.
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*note that it is entirely possible that Child misunderstood what [Elder Sibling] had to say on the topic or that [Elder Sibling] had never ventured an opinion on the topic.