I'm really tired of manga that portray comically evil actors with no repercussions whatsoever. It's stereotypically Japanese.
Putting on "actual adult" hat: this single war-speech/series of actions shows genociding the entire beastmen species probably is warranted, since they are shown to (routinely) consume humans as food. But let's put that on the shelf for now. This isn't even considering it as an emotional kneejerk or torturing their entire species; they are literally a existential threat if any beastman woman or child survives.
Assuming they are permitted to continue to exist: at a minimum it would be summary executions of all leaders. Think Nuremberg Trials post-WWII. It's wasn't even a question of "if" to execute. It was a question of "who" to execute. Who knew what and when. And the leaders most certainly knew. (And we as audience saw they knew via exposition.)
Even the quote-unquote "pacifist" beastman leaders (like the cow lady) that did nothing, are not blameless. They cannot be jailed, as that uniquely French concept doesn't exist in this not-our-world fictitious universe. Where the concept of "war crimes" doesn't exist, as a purely modern fictitious treaty construct. Meaning: summary execution of any beastman leader regardless of degree of contribution. Their families, anyone intending to retaliate, or with capability to retaliate.
Part of not crossing bright red lines is, the enemy will feel permitted to do the same. If not worse in retaliation. Entire military doctrines about Rules of Engagement are based around this, or in flip case, outright overmatch ignoring this as a form of rule through terror. The whole concept of "modern limited war" began because the atrocities of "total war" were so horrific, we agreed as a species to never touch upon them again.
...but since this is a JP manga, they'll completely gloss over that and use some "nakamah powa" ending where the beastmen are forgiven, or, in fact, were good guys. What a twist! How humble and kind!
Just for once, I'd like manga authors to actually consider the implications of their characters' actions. And actually follow through with the logical outcome.