Tbf, he's not wrong. Demons are immensely dangerous to every living creature, including themselves, which is why they were never united thus far. Only under the human threat, and ironically, using them as a model of sort, did they manage to properly group together.
Forming their own nation, and being independent, is the best way for them to be taken seriously, as people, of their own culture and sovereignty...Otherwise, they are either nomads, or refugees that flee to human territory, and that leaves them to the whims of humanity.
So, in short, I disagree...I think he had the right idea, to fight for a demon nation. Is it odd that a revolution of sorts will require sacrifices? Not really.
That being said, I do agree that he's incredibly disagreeable. It's hard to truly root for him.