So when is the best moment to discuss instruments and powers a government is collecting, before or after they have used them to install an authoritarian state?

The threat of authoritarian regimes is very real for all democracies. We are one of very few nations with a long history of democracy to have not had authoritarian regimes take control. Modern Western Society is not special the U.S. is special in this reguard. France, England, Germany, Italy, Argentina, Brazil, Mexico, Spain, Chile have all had authoritarian regimes. The other major democratic states have all existed for a shorter period of time or were part of one of these states as a colony, when they were a democracy.

The problem is how much power is to much power. The issue is not in the power a government holds but that it grows endlessly. If the powers of government are never being reduced some day the powers will become to great. Even if a government had to much power it does not make it an authoritarian state. This is a situation that then is only maintained by formalities. Does everyone use a fork correctly? Do people still take their hats off when indoors? Formalities change, it's that simple. One regime may barely use the instruments of power they posses but another may use them with far less discretion.

This is all without crises, mob mentality and demagogues. We have no way to predict the future and what is reasonable today may not be in the future. What is condoned, acceptable and expected of ones government may not be the same in the future as culture, attitudes and mood change overtime. That is why the discussion of the scope of governmental power is an ever present one that cannot be ignored even for a moment. So that just because a government is trustworthy today doesn't mean that that situation may not change, it also does not mean that those changes will be opposed. Further just because a democracy acts within the democratic institutions , does not mean it is correct, which is doubly true for one without protected open discourse. Democracy merely can divine through it's mechanisms the will of the people and only an educated populace with free and open discourse can ever hope to come together to lead it reasonably. When it becomes okay for a state to take most of the open discussion away democracy already does not exist, for it is the will without understanding.