Commentary: Bigotry stopped Americans from intervening before the Holocaust. Not much has changed

A ruthless dictator unleashes terror on his own citizens. Those fleeing elicit sympathy - but encounter obstacles to entering the United States. Americans learn of mass killings, but their moral revulsion doesn't easily turn into policy or military intervention. One thing remains consistent: America doesn't want refugees, at least not of this ilk; those people aren't welcome here.

Historians like me are wary of the adage that "history repeats itself." But comparisons and analogies help