In a hierarchical society such as ours, anger is a privilege of rank; parents & teachers can get angry at children; if children get angry, they are often punished. In most organisations, those in senior positions are allowed to get angry at junior staff; if junior staff express anger at managers or executives, they will often be disciplined or dismissed.
This leads to a lot of people having repressed anger. This anger doesn’t go away, it simmers below consciousness looking for an outlet. Repressed anger is very useful to demagogues; if they offer low status people something to get angry about & give them permission to be angry, all that anger has an outlet & has been weaponised in service of the demagogue & potentially against the interests of the mob.
Anger activated in this way leads to people using their political power against their own interests. It can lead to catastrophes like Brexit & President Trump.
We can guard against being manipulated by demagogues by practicing emotional intelligence; acknowledge the injustice & injury that causes anger while consciously choosing not to direct that anger when that might not be in our best interests.