Catholics around my parents age (late 50's) were told during the cold war that Communists were evil and were committing atrocities because they were godless. The communists had no moral fiber as a foundation and therefore were prone to attrocities that good catholic nations (the catholics believe they have the majority in the US) are certainly not. All of the US's atrocities are defenses to the godless nations attacks on what makes us Americans: freedom liberty pursuit of happiness. They of course passed all of this down to my generation.
If you want to work from effect, Vietnam is always a good place to start. My parents were and still are extremely conservative, but they still have a soft spot for vietnam.
I would strongly suggest working from morality of course (see above)
I hope this perspective is helpful.