I actually see a bit of a parallel between Kiroumaru's stated plans for WMDs and where he, Saki and Satorou find themselves right now. Kiroumaru claims (and we have little reason to disbelieve him now) that he was trying to create a
MAD scenario between his tribe and the humans to prevent the Giant Hornets from ever being wiped out. The humans would still retain all of the power, since there's still no other way for bakenezumi to fight them, but the psychobuster would give the humans pause if they ever wanted to actually
wipe out his tribe, because then Kiroumaru would have nothing to lose. As things currently stand, the Giant Hornets' very existence depends on the whims of a fickle and fearful tribe of mortal gods. The assurance of a future for the clan would probably be worth the lives of a great many scouts.
Interestingly enough, this is exactly the situation they find themselves in now: Yakomaru has them beaten. He holds all of the cards (or so he thinks), but he doesn't dare to actually finish them off because if he did, they would bring down the caves and kill him too.