so they didn’t know they would be killing people? That the war was unjust? Have they paid attention to any war the US was in before signing up for the least moral army in the world?

Exactly my point. Propaganda and group pressure are strong factors. Army recruiters don't exactly go around showing you videos of war crimes. This does not absolve anyone from making their own decisions, of course. And once you are in, getting out is hard, and you are actively pressured against it.

yeah they run for congress

they do not “believe they did the right thing”

Aren't those two statements contradicting each other? The guy you quote seems to believe he was doing nothing wrong.

My statements may be a bit generalising, but I would bet a surprisingly large chunk of people who are part of war crimes and abuse do not believe they were in the wrong. Now, why they do this is a good question, maybe it is the mind trying to protect itself, maybe they are really the kind of psychopaths that are usually kept in check by society.

the gas chambers famously weren’t ok after, but a complete mess

I would love to see some sources for that, because from all the anecdotes I have heard, many people who were actively involved in the Nazi genocides were mostly concerned about persecution.

no abuse similar to abu ghraib or the concentration camps is known to me

A statement I would have expected more from a .ml user.