>>44231
Large part of the book is about the factors make killing possible. Those who did not feel remorse were better at denying the humanity of their victims.
Also he might just exaggerates, he noticed a couple of soldiers happy about the thing and this is what he fixated on, not noticing other people's remorse. He was in emotional turmoil where only very opposing reactions could have stood out for him, while he was preoccupied with his own feelings. Then he just generalized, that everyone was like that.
Plus the impact of the act can hit later. Like for Vietnam veterans.