How many so-called 'good people' were hoodwinked by National Socialism, Leninism and Stalinism, and many other cases of sociopolitical change and reform that from a selective view seemed to be a progression towards a better society?
Politics is in part about truth, however, it is as often about personal and ideological desperation as well. The Early signs from Nazism wasn't that of camps and murder, 'the Soviet project' was praised even after the bloody civil war, purges and show trials. It seems that many would rather believe in the perfect future than treat reality with the kind of harsh scepticism it deserves.
We see much the same of Islam, with many Muslims who at least don't ignore the actions of ISIS but they may quietly desire a new Muslim super-power and religious authority to usher in a new golden age of the faith. In that way, the examples of religious fundamentalism across the world are a kind of inspiration, much like many-an-old-Marxist was hopeful that the Soviet project, despite a shaky start, would offer up fruit.
You can find western communists who seem to be unable to accept the insanity of North Korea, any bad news is called capitalist propaganda, and so easily dismissed by all true communists. They, as with many Muslims, Neo-nazis and other ideological views, think we in free societies are living on borrowed time and out of the chaos, they'll bring about a better world. I can only assume that something about the idea of knowing the ultimate truth breeds arrogance and even greater credulity as they swallow lie after lie from their comrades in arms. As if their conspiratorial tones are more than musings of those who dream of their ideological victory.
It's actually odd that rather than respecting facts first, many millions of people would rather believe in the coming of their hopes by some kind of inevitable process. Instead of noting their errors and noticing the irrationality they hold dear they would rather ignore those things that may move them out of their comfort zone. I suppose I've been too narrow, and as I ponder this I can imagine this frame of mind with any number of beliefs.
In general, when reason leads you will discover, and when faith leads you will make excuses.