I don't think anyone is insinuating that Bitcoin will stop all violence and skirmishes. The argument being made is that state actors cannot use deflationary currencies as a tool to socialize/amortize the costs of large scale wars.
Demanding war and socializing the costs is one thing, but what would happen if everyone used Bitcoin instead of Government fiat, and thus governments would need to propose legislation to fund a war through bonds or taxes instead of simply inflating the monetary supply? From what I understand about human nature we tend to be selfish and hypocrites who prefer other people to pay for our wishes and often have higher priorities than war to spend our bitcoins on.
What we are also proposing is that the adoption of any crypto-currency which makes it more difficult for states to tax and regulate also makes funding such wars more difficult as well.
One argument that would be valid against my position is if state governments consistently become proficient at stealing the private keys as they have done a few times in the past than Bitcoin could be used to fund their adventures. Hopefully, hardware wallets and multi-sig will assist in deterring these unethical actions committed by states.