Any financial system can be damaged by someone willing to destroy a massive amount of their own wealth. But self-interest usually discourages people from doing so.
Nice quote, obviously the bigger the economy the more money you need. Anyone with the figures on hand and the brain to do the math want to figure out what would happen to the USD if Bill Gates burned all his or decided to inject it in to the economy. We can pretend that he has liquid cash for whatever his net worth is. Obviously his liquid capital is a lot less.
If he were to sell all of his investments, convert to cash, and burn it all in a public pyre; then all of the remaining cash in existance would be, temporarily, slightly more valuable. Not to any extent that would be noticable, however, and only for however long it took the Fed to replicate those destroyed bills.
As for injecting it into the economy, that is exactly what he does with most of it. That's what investing is.
