[eivarv]

I think you'll find that psychological health has little to do with what people can convince themselves of, or convince themselves to do - i.e. you can't explain away Daesh (or WWII nazis, etc.) with mental illness.

Their actions could absolutely be called rational and logical if you were to accept their premise - which is what I'd argue is irrational.

[mercurial]

You don't even need a Godwin point for that. Nobody was calling Air Marshall Harris, well-known for his strategy of carpet-bombing civilians with incendiaries during WWII, "insane" or "irrational". Instead, they gave him a bunch of medals and made him a baronet.