The etymology of the word "religion" is in dispute, but the fact of the matter is that most people "have" a religion. Most people subscribe to a codified system of beliefs that serves as a base for their moral and ethical behavior, and as a way to identify with and to act in concert with other people who share the same beliefs.
What does this have to do with a progressive vision of humanity? Quite a lot I think. The very nature of progressive thought is intimately tied to the notion that mankind is perfectible, or redeemable - that through reason, and reasonable interaction, human beings are capable of creating a society that will benefit all its members.
This progressive notion is in no way traditional, having been in existence for less than 300 years. During that time, progressive ideas have often been influential in determining governmental policy, but progressive thinkers and activists are new-comers, mere raw up-starts, in relation to belief-systems that have existed for centuries, or millenia previously.
These systems are well rooted, but we are not. Ancient religions have seen governments and even empires come and go, and yet they retain at least a semblance of unity and continuity. That is why people have faith in them.
The average "uneducated" person who is religious has little or no faith in political solutions to the world's problems, perceiving (often correctly) that politicians, and political regimes in general, have no moral integrity or backbone whatsoever. So this average religious person will look for leadership to a "higher" authority. He or she will look to a time-honored, and fully integrated system in which difficult moral choices have already been decided, and within which it is possible to live without any outside input.
Religious people (by and large) are insular, by choice. Their "Truth" is absolute and fixed, invulnerable to, or at least well-protected from the ravaging winds of change that are bound to beset the unfaithful, the heretics, and all those who choose not to be enfolded within the comforting arms of the (Church, Synagog, Mosque) community.
Which leaves us, as progressives, somewhat out in the cold and vulnerable. We have no comparable institutions in which to commune, and seek shelter. We have no ceremonies, no rituals, no mythology to bind us together. We have only our precious individualism. This is not to say that we are less spiritual than religious people are - on the contrary, we are in general far more so. But we are operating at a distinct, and possibly crucial disadvantage.
We should recognize this disadvantage, and do all we can to counteract and minimize it. Above all, we need to build and treasure a sense of community. How can we do this, without the ritual and ceremony, without the physical, sanctified gathering of ourselves that Religion enjoys as a matter of course?