Well you know I think that canonically "conceit" is associated with disputes.
"The Good" was a subject of Plato's. When I was a teenager I found it unsatisfying as "logic" because I think he doesn't really define "good" -- or uses a circular definition -- but says that he and who he's talking with kind of know it for ourselves or recognise it when we meet it.
Also "the" good -- as a noun not just an adjective -- is obviously reified. And it's a dichotomy ("good or evil", "with us or against us"), and I beware of dichotomies.
Now I think that Buddhism does define "good" -- the precepts and the perfections.
But personally I think it cleverly substitutes "skilful" for "good", asking not only whether an action is good but whether it's skilful (or combining them as "skilful virtue"). To me the word "skilful" implies context, forces you to ask what's the goal -- like, "skill at what: making pottery? -- and there is a specific "goal" implied in the suttas.
Remembering the "goal" described in the suttas might be one way to "keep it under control" -- to avoid excess? Getting carried away?
γνῶθι σεαυτόν, "know thyself", as well as μηδὲν ἄγαν. Because of some past experiences, I don't especially trust myself: I've experienced being emoted by, exulting in, caught up in, carried along by, like fascist ritual -- exulting in the feeling of belonging to a power, a chanting crowd -- even a tight rugby scrum! -- which I'm in and which is greater than me, which amplifies what I'm doing. Since then, I'm wary now if I feel that effect.
I think the suttas say -- and experiences says -- that we're not supposed to identify. There are good and un-good (skilful and unskilful) thoughts and actions, they come and go, the doctrine says to recognise them and to foster or dismiss them as appropriate. Knowing that I'm theoretically susceptible to fascist propaganda doesn't make me good or evil, it makes me watchful.
The other thing is that the Buddhist precepts (perhaps the Vinaya, for monks) provide something a "bright line" for judging actions. I was trained to handle firearms for example and taught a lot of history including military, but now I avoid any invitation to touch a firearm, even for target-practice -- it's not that I don't know how to, it's just I don't foresee any particular good (only a waste of time) and I feel that my never having a weapon at hand is a fail-safe and a good reminder even in case of temporary madness (though I'm happy to forgive the Dalai Lama's carrying one as a disguise for his escape).
Self-image does come into this too. My wife declined weapons practice in Tai Chi, saying she found it un-lady-like (perhaps an example for me); and told me she was glad when I became too old to be conscripted; and she asked me to remain vegetarian. I think these are conceits -- not worth identifying with, and impossible to keep in mind continuously -- but also harmless and so not worth getting rid of.
Which leads to another Buddhist doctrine, "harmlessness" (ahimsa). I think that Buddhism is less "extreme" that Jainism in its doctrine of ahimsa, a middle way -- which doesn't mean "harmless but occasionally being violent", it means "avoid being violently harmless".
Lastly I don't know what to say about the poor soldiers caught up in this war. I don't entirely respect what the suttas say about wheel-turning monarchs and defence of the realm: I suspect that was "retconned" for Ashoka. Instead I'm reminded of the very little I know of samurai, from wholly unreliable sources e.g. manga (and the occasional Zen story) -- I used to wonder how they could be Buddhist and deadly -- something to do with accepting going to hell perhaps (as if that's the worst that could happen).