In particular, I've really disliked the "Never Again" slogan for many decades now. It seems clear to me that people living in nation-states really like committing genocide and that nothing in the international system that we've set up really restrains people from genocide. There's something extra horrible about a "never again" slogan that is broken again and again.
The US bears special responsibility for ending whatever rhetorical commitment there was against genocide because we so obviously support death squads, official torture, deadly borders, forced relocation, concentration camps, and other adjuncts or preliminaries to full genocide and because the US was a primary author of the post WW II settlement that really made a commitment against it.