The engineer in me reacts to words like "impossible"
As a human, I can easily disrupt bitcoins at present with a large enough wad of cash.
Yes, but what's so special about cash? it's just a type of asset; you're simply reaffirming that if you are using something to purchase bitcoins, the notional value of BitCoins will be increased because of your willingness to exchange it for a different asset... you could put a car up for sale with X amount of bitcoins accepted as payment, that too would have an effect on its value, however, if your price was way above or way below the current averaged value, your distortion would be short lived.