The core of progressivism is radical egalitarianism, a utopian, immature, idealistic, and impractical version of equality popularized today as “fairness.” It is the Liberal/Progressive’s most highly regarded ideal above all others. Quite possibly, among many of this group, it is their only ideal and it is often pursued with a religious-like zeal.
It’s the product of a primitive part of the human psyche — the collectivist way in which groups organized themselves when humans existed primarily in small bands or tribes. Psychology studies have documented the immature sense of equality or fairness that is operational in 4 year olds, where rewards of treats are given for completing certain tasks. When subjects were given the authority to change the amounts of the rewards obtained, the preschoolers invariably redistributed them in equal amounts regardless of the number of tasks completed by the individual subjects who earned the rewards.
This immature sense of equality or fairness also has a visceral appeal to many adults as well, especially those dictated primarily by emotion and “feelings” rather than by reason.