Fortunately the destructive doves weren't able to fool FDR about the Nazis. "You can't turn a tiger into a kitten by stroking it," he once said — but the pious nincompoops and delusional intellectuals were persuasive enough here and abroad so that France, Britain and the United States were unable to step while Hitler was still weak and prevent World War Two by enforcing the peace.
Had these people wised up and supported moderate programs of rearmament in the early 1930s and insisted that the western democracies take a stand against Hitler early on, there would have been no Nuremberg Laws, no Holocaust, no mass terror bombings of European cities, no Stalinist occupation of central Europe — and no Cold War.
Morally of course this was nowhere near as bad as what the Nazis and Communists did. The peaceniks didn't will the slaughter of millions of innocent people: out of ignorance and conceit they merely created the conditions which let it happen. But while the peace movement wasn't as evil as the dictators, the dictators could never have achieved their goals without their sanctimonious and timorous enablers in the western world.
It is just not true, historically speaking, that 'peace movements' lead to peace or, for that matter, support policies that will bring peace. More often than not, the opposite is true. Winston Churchill was a grizzled old British imperialist of the worst kind, but if Britain had listened to him instead of to its peace campaigners in the 1930s there most likely would never have been either a World War Two or Cold War.
Hopefully we're not doomed to repeat this lesson.