Sickness in US society will not be easy to cure

For a long time, people in the United States took pride in the belief that one of the things that made their nation great was a system that was designed to encourage principled disagreements so that people could achieve consensus through reasoned debate.

"I disapprove of what you say, but I'll defend to the death your right to say it," as French philosopher Voltaire put it.

Yet their faith in that system seems to have wavered in recent years amid the widening social, racial and political divides in the country.