Earlier quoted context omitted.
That's because civilian protections where only added in 1949 to the Geneva Conventions. The Geneva Convention as-of WW2 would only be applicable to PoWs, not civilians.
To be fair I don't think anybody saw systemic violence upon civilians during a war between states (as opposed to a civil one) as a realistic possibility during the inter-war period. It was well outside the customs of war in our corner of the world at that point. The national-social cocktail completely tore apart common decency.
Really? Atrocities against civilians in war were common even then. No need to look further than e.g. the colonies.