Once humans have made a decision, they find it uncomfortable and difficult to change their minds.
Brexit is a good example. You only have to look at twitter to realise that whether you voted Leave or Remain, you probably are following other people with referendum views which closely mirror you own.
Don’t believe me?
Then go onto twitter and search out a Leave supporter (or Remain supporter), and take a look at who they are following, and what tweets they have liked or commented on.
Generally speaking you will see that they are confirming their voting choice was, in their minds at least, the correct decision.
Whilst ‘Confirmation Bias’ may be what most people do, it is in my opinion a valuable skill to be able to see opposing sides perspectives, and be open to a possible change of opinion, if convincing evidence is put forward to support a change.
This is obviously a hard thing for humans to do.