How exactly is this an argument of rationality versus emotion? Arcadius himself gets this wrong, his view that worse things are happening on a grander scale worldwide is still an emotional response. We don't view genocides through a statisical prism, we relate to the individual stories that must occur within that and are horrrified (emotion) that this was a matter of policy or cultural circumstance where it happened. If we are detached from the individual cases that drive us emotionally we have no logical reason to disagree with systematic offences that may occur through our indifference. I feel a lot of people are misrespresenting this as support of moral deviancy in quite tactless ways but Arcadius' original dismissal of the smaller event in favour of larger ones would in of itself make it impossible to tackle the larger ones. We have no reason to oppose any of this without emotion, which we can only relate on smaller scales (that's what are brains are wired for).
Otherwise we're Stalin.