if it should prove as disruptive as some people hope
Bitcoin would still be useful even if there was only 1,000 BTC in circulation. Or 1.0 BTC, for that matter, as Bitcoin currency is divisible to eight decimal points. It might be slightly less useful if it couldn't be divided further, but it would still be useful.
If the rich entity were to then simply destroy these coins (and it was verifiable that the coins were truly destroyed) then the exchange rate would stabilize and Bitcoin could continue being used. In that scenario we'ld have to get used to referencing prices in satoshis (0.00000001 BTC) and not BTCs themselves though.
If the rich entity were to start selling the coins instead of destroying them and was to put them back into circulation there could be disruption. That could cause exchange rate volatility or price inflation even, depending on the rate they were reintroduced and the demand for them.
So yes, bitcoin is vulnerable to a rich entity hell-bent on causing grief to the currency. But doing so would take an enormous amount of money ... and spending $2 to save $1 isn't a rational economic decision.
I can't see any justification for taxpayer money being used to do this and I certainly can't see any corporation explaining to its shareholders why this was the best use of their funds either.
That a bitcoin is worth as much as the cost to produce / mine it is just a proxy value - you can't use a bitcoin to get back that amount of energy / computation power - it's all backwards.
Unlike gold mining or production of other commodities, the cost to produce a new bitcoin rises and falls -- it will equilibrate with whatever the market value is for that bitcoin (as difficulty follows price), and not the other way around. In that sense, you are correct -- Bitcoin is backwards. It does break the rules. Isn't it a novel concept!