I'd say the post-apocalyptic The Mist (2007) handled this quite well. Based on a Stephen King novel, it tells the tale of a band of ordinary people of all races and genders who hole up in a supermarket ... and rapidly abandon all logic and reason to form a quasi-cult, turning quickly on the logical and rational people who they eventually blame for the acocalypse.

The point is that ordinary people will rapidly fall in line behind whatever demagogue has the power at that particular moment in time.