Speaking in support of military action against Syria, Alexander Bolton of The Hill reports, Senator Harry Reid brought up the example of Nazi Germany and the Holocaust:
“Millions and millions of civilians and prisoners of war were murdered by gas in Nazi death camps, Treblinka, Auschwitz. ‘Never again,’ swore the world. ‘Never again would we permit the use of these poisonous weapons of war.’ ”
Reid really poured it on, as Shane Goldmacher at the National Journal writes, when he:
...read – twice – a quote he attributed to Dante: "The hottest places in hell are reserved for those who in times of great moral crisis maintain their neutrality."
It seems, however, that the quote cannot be found in any Dante's works. That, anyway, according to this exchange in Snopes.
It's a good line, though, and the confusion has a fine pedigree. It appears its misattribution can be traced to John F. Kennedy.