Right, clearly burning a million or perhaps even quite some millions would have a negligible effect on the currency, similarly millions in counterfeit money would have to be circulated to actually destabilize the currency (that's assuming the dud notes aren't noticed first).

Clearly, in modern times in modern democracies it's very unlikely that in any practical scenario that some entity would be capable of unofficially adding or withdrawing enough money from a currency to actually destabilize it, moreover in such an event the central bank/government would be onto it in seconds.

It's however an altogether different scenario if the citizenry somehow has the perception that the currency isn't exactly what the central bank purports it to be. Just the notion that something may be wrong with the currency could destabilize it, hence hellishly tight laws to ensure this never happens.