How would a central banker know the "right" amount of electricity a competitor should use? After a while, you notice the patterns of smear techniques from the central banking advocates. They lost their credibility long ago. People might think I mean 2007 ("too big to fail" and all that), but where I live the locals don't trust the banks because of stories from the Great Depression in the 1930s.
Nice clear reasoning.
Let's leave aside the fact that finding difficult hashes of block headers (i.e. mining) keeps your money safe from rogue miners attempting to re-write the blockchain (i.e. this is what makes Bitcoin uncensorable, so more mining is better, not worse). Let's just park that issue, despite how much more honest and transparent Bitcoin is than central banking fiat as a result.
So, Christine Lagarde doesn't like that Bitcoin costs energy to produce. After all, the IMF and other fiat printing central banks can produce new money supply for a disappearingly small fraction of what that new fiat money is valued at.
But that's essentially the problem underlying the entire world financial system: the privileged ability to create money (and debt) at will has, unsurprisingly, led to a severe lack of discipline amongst those privileged to do so. Anyone familiar with the history of such abuses of monetary levers of power knows how this story ends: badly, and in many flavours of badly. And the current abuses (in fairness, only sanctioned by IMF hubris so they're only indirectly responsible) are probably the greatest ever seen. It's prudent to expect the economic fallout to be on a similar scale.
So no Christine Lagarde, forcing discipline on the monetary supply using a finite and tangible resource is not a problem, it is a virtue. Your practice of approving fiat money printing at essentially zero cost (with correspondingly zero discipline) is a serious threat to the world economy, and the lives of the people who constitute it.