Technically the concept you’re referring to is totalitarianism.
Generally speaking that’s the view that there is one truth, one set of morally-correct beliefs, and that because What Is Good is known, it can be assumed those who don’t agree are Bad People.
The basic seed of totalitarianism is this idea: “We know everything that needs to be known”
An example of a totalitarian culture is Nazism: they thought that they’d worked out The Truth and that gave them the confidence that they were doing the right thing even as they did horrible things.
Another view on totalitarian belief is this common argument against capital punishment: “Given there are errors in determining guilt, a system of killing people determined to be guilty, will in fact kill some innocent people.”
That’s an anti-totalitarian argument. Basically it says “Given that we don’t have omniscience, let’s take it easy on the drastic action”
The totalitarian view on capital punishment relies on this implicit argument: “Our courts have determined that guy is guilty, and our courts are always right, so the only ethical move is to kill him”. Then you might ask “why’s it okay to kill that guy but not other people?” and the totalitarian say “that’s different, because the first guy is guilty and the second guy is innocent”.
It’s that certainty that defines totalitarianism.
And the way it leads to dictatorships is this: If determining the correct move is a finite process that proceeds deterministically from observations and the already-determined set of moral rules, there’s no reason to ask multiple people’s opinion about this law. Therefore it will be law because we know it’s right.
The non-totalitarian stance is open to new information, and doubts the ability of any one individual to have final knowledge of the right move, and so polls everyone on major decisions. ie democracy, or the distribution of power.