The Left is totalitarian in its nature
The human species produces a certain percentage of scum. That is the way in which I have understood the world my whole life
Therefore the vast majority of the people who affirm leftist beliefs think of their views as the only way to properly think about life.
Governments grow as God declines, in both Europe and the United States
American is deteriorating because it is becoming like other countries
Most activists on the Left believe that they, not only their values, are morally superior to their adversaries. Therefore, coercing people to adhere to 'progressive' values is morally acceptable, even demanded.