Aside from greed, mental disorders and cruelty, the main cause of conflicts between human beings is the differences in their values and viewpoints. Such differences may simply be expressed as friendly disagreements, but when emotions become intense, and the issues are perceived as very important, the parties involved may turn to verbal insult or even physical violence. The underlying reason that some people insist on the veracity of their own viewpoints, and at times resort to force to convince others, is self-righteousness.
Often self-righteous people believe they are morally superior to others and, for this reason, they have no tolerance for different views. In their minds the people with opposing ideas are so wrong that must be crushed and eliminated. The communists in Soviet Union and China were such examples.
Currently we have a group of self-righteous liberals in this country who believe socialism is the cure for all of our economic problems; the U.S. is afflicted with systemic racism; the police force in the cities should be replaced by social workers; the borders should be left open; the unemployment benefits should be given indefinitely; the colleges must be tuition-free; there would be no problem for the government to borrow money and give away entitlements; and so on.
The self-righteous liberals label any objection to such proposals as immoral and an affront to democracy, disregarding that some of their ideas could fundamentally be detrimental to the well-being of our society. In the mind of morally superior self-righteous individuals, other people are not capable of taking care of themselves and need constant government assistance (obviously with our tax money!). Perhaps they need to be reminded that it is easy to be benevolent when someone else is providing the funds.