See this is why i love this mange, it straight out addressed the moral debate it ignited, this is such good shit. I am glad Harukiyo is not buying, and who would? his reasoning is a bit out there, however....
There is a demon that laughs on the battlefield, Inuzuka has the powers of teleportation, hyper luck, omnipresence on the battlefield, and omniscience of war affairs.
So if you tell me that he can posses or brainwash people and make them act crazy i would believe it, hell we already saw him messing with Tamara on the underground waterway.
The only problem is Kai himself, since he clearly lost his mind, he may just be talking bullshit to defend his actions, but if Inuzuka did end being the one behind this, i would believe it too, that wont even be the weirdest thing he has done.