If it is legal for the state to aggressively censor what the state deems misinformation in the case of a real crisis, it is similarly legal for the state to aggressively censor true things that the state deems misinformation in the case of a manufactured crisis.

That's the issue: we do not trust the state to be impartial enough to decide what is or isn't misinformation. Remember when they lied and told us not to wear masks so they could hoard them for healthcare workers? In that instance if they had been "much more aggressive" as you advocate, saying the true and correct statements of "this is an airborne respiratory virus and you should wear a mask" would be subject to such censorship.

Given that we've seen governments carry out all manner of atrocities (eg the US CIA torturing people in the wake of 9/11 for a recent example, or the Third Reich's famous death camps) throughout literally all of human history up to and including present day without exception, by both "good" governments and "the bad guys" (also without exception), why on Earth should we allow such organizations the power to decide with force of law what is or isn't true?

A lot more people will die from direct and intentional actions by government than will die from misinformation.