When emotion takes hold, humans tend to act like lawyers, furiously working to justify their beliefs, cherry picking their evidence. This tends to be exacerbated by the echo-chamber of the internet media, but this tendency existed long before modern times. Chis Mooney suggests that we are wired this way, because we have evolved to act quickly. The following PBS video uses the examples of global warming and the purported end of the world to explore the way many people are wired:

Watch the full episode. See more Need To Know.

I agree with many of the points made in the above video, but I there is also a well-documented social component to “motivated reasoning.” If trusted others are believing X, you will be tempted to do likewise.