Can we edit the poll to add a 'That's a Stupid Question' button?
Well, I agree that this is a rather stupid question, but I think it would be a wise thing to do to explain to him why it really doesn't matter whether those coins are still available or not. Also it is very important to understand why this really wouldn't hurt Bitcoin by undermining one of it's key principles.
Central banks hold 1/3 of world's gold reserve, should they destroy them? What if they dump all the gold on market and crash the gold price to cents?
Even central banks decided to dump small amount of gold, they would still do it gradually, to not affect the market price too much