Independence

On July 4th, my son and I had a conversation that went kind of like this:

Me: Why is this fan missing its cover? (As I pick up a 3 speed, white plastic fan, about 18 inches tall. Fan is lying on side on floor and it is running.) If we can’t get the cover back on this fan, you can’t have it in your room.
Him: (Tone is sarcastic, but not exaggerated) Oh, yeah, I wouldn’t want to get injured by this flimsy plastic.
He wants to touch the spinning blade to prove how silly I am, but I see the tiny hesitation in him.  I set the fan down, while I find the cover on his floor. Now, my son sticks his toe on the running fan blades for a couple of seconds and nothing happens to him - just that strange noise of the spinning blades hitting calloused big toe.
Me: Sorry. (My tone is no nonsense, stern, dictatorial - depending on your perspective) If we can’t get the cover back on this fan, you can’t have it in your room.
Him: (Repeats the following a few times). Describe one specific scenario where that fan could hurt me. Seriously. What could happen? I guarantee you 100% that this fan will not do anything.
Me: You cannot guarantee this 100%...
Him: Well, can you guarantee that my bunk beds won’t injure me?
Me: That’s why I wouldn’t let you sleep on them if they were damaged.
Him: Can you guarantee me that this bookshelf won’t fall? (He asks this of several other items).
We haven't been able to reattach the cover while holding the fan in the air, so I take it out of his room and set it on the kitchen table so that I can clean off the dirt and try to replace the cover. He thinks I’m taking it away, and is appalled that I’m really doing this until I explain that I'm still trying to fix it.  Nevertheless, he continues his challenge even though we don't know if I'll actually take it away yet.
Him: Can you think of one scenario in which I could possibly get hurt by this fan?
Me: (no answer)
Him: It’s quiet, it works well.. Seriously, describe how this fan could hurt me if it doesn’t have a cover.
Me: Can I record this conversation?
Him: Name one scenario... (I won't bother to finish this line, but he did.... Then I think I repeated by question about recording the conversation, and I was tempted to do it.  So he repeated his demand for a specific scenario of gore caused by this cheapo fan. . . )
Me:  L, have you ever heard of picking your battles? Is it really worth fighting for the right to keep this fan in your room before you even know the outcome?
I can’t remember how it finally ended – 
I explained “picking your battles” and that got at least a wee bit of attention from him. 

I really couldn’t think of any specific “scenario” while my son was badgering me for one... I mean, I toyed with the idea of saying the cats might be injured -- HA HA.  I chuckle every time I think of it.  L would have lavished scorn on any "kitty" scenario.  Fortunately, I wasn’t desperate to win that point. 
When the conversation ended, I really could see a scenario... but by then I knew that, if I were so foolish as to say one word about it, I would be responsible for opening up this dead-end in human communication.
I got the fan cleaned up and put the cover back on.  By then he was playing a video game, but I told him I was putting it back into his room only for as long as the cover stayed on.