Ideas about "us" and "then", which are reinforced by social norms and by a self serving media may well lead to results that range from the merely unfair to the catastrophic.
Adults are not to be treated as children
Trust is a valuable norm. As a concept it rests on one of our strongest behaviours - conditional behaviour. People will punish free-riders even when it costs them to do so.
Another characteristic is "confirmation bias" - the tendency to interpret new information as support for our existing beliefs. We also suffer from loss aversion, fierce rersistance to losing what one already has. For people on the margins of survival - that made sense.