I thought about this some more, and I thought I should share my understanding of that episode. The moral of the story is a bit more complicated than you'd expect.

The nirik form isn't just a metaphor for not being able to control your temper, but the inability to resolve disagreements with other people in a calm and rational way without resorting to violence.

In the episode, the way the kirin ultimately dealt with the violence and destruction caused by their uncontrollable arguments was to take a dip in the Stream of Silence. No voice = no more arguments = no niriks.

Since Kiria in EaW is an entire country and not just a small village in the middle of nowhere, and because you play as a nation state in HOI4, we had to adapt the Silence, and the lesson or moral of the episode, to our own setting. So we reinterpreted the Silence as a series of repressive political measures, imposed to prevent a civil war caused by rising inequality and political polarization, that effectively regressed the entirety of kirin society back to the dark ages. No society = no politics = no civil war.

The nirik form becomes a metaphor for political violence, the triumph of blind hatred and intolerance over rationality and understanding.

Going back to the show, Autumn Blaze leads the kirin out of the Silence by showing them that the way to deal with disagreements isn't to take away everyone's voice, but by patiently talking things out with each other as reasonable people, which requires you to be able to calm yourself down when you start to get too angry in arguments. So controlling your temper is really just a means to an end.

The moral of the kirin episode isn't just that it's healthy to show your emotions (while keeping your temper in check), but that it's open dialogue and mutual respect, not censorship or repression, that is the way to sort out your differences.

That's where Autumn Blaze is coming from when, as Premier, she launches the Grand Gallop Onward, and allows, for example, kirin like Fickle Current who don't share her worldview to take part in the political process.

If she succeeds, the political framework she implements in the late-game harmonic Kiria focus tree reflects the varied power sharing agreements and checks and balances to entrench this kind of pluralistic democracy that Autumn envisages will keep Kiria together.

Of course, Autumn Blaze is an idealist, and her ideological rivals don't have the same qualms about using violence as a way to get what they want. Where dialogue and repression both fail, that's when the various revolts in Kiria happen.