Here's another case one of those Facebook walled-garden discussions that really needs amplification and a public airing.
The subject is membership. The issue is on what basis can a congregation admit members? And in particular, by whose authority and volition. Is a person's membership largely the will of the person who wishes to join? Or is it a status conferred by in an authority of the church: its governing board, say, or the congregation in meeting?
The answer you think is right says a lot about what you think the congregation itself is. In Unitarian Universalist circles today congregation has become synonymous with church, society, parish or fellowship. In historical practice, however, these were each different things.
A congregation is who met. The church is the company of believers, governed by spiritual leaders -- the minister and the deacons -- and it might shock you to know that many Universalist "churches" never organized one. The society is the parish without particular, reinforced geographic bounds, though that meaning is now especially obscure. Both served as a kind of moral, educational and religious (almost "religious but not spiritual") public utility. Preference for the society/parish over the confessing church is the characteristic the Unitarians and Univeralists share. Indeed, share it so deeply that the distinction with church-as-company-of-believers is either blithely forgotten or hostily deprecated.
I contend it's what gives us our curious something-for-everyone institutional chaplaincy feel. And it's what makes some of our attempts to carve a unified spiritual community out of this nexus so awkward. We've believed the jargon, that we are a community of faith. That we have a "saving gospel." (OK? What is it?)
No, we are more like a community of people with faith, than a community of faith. Not the same thing, and not a bad thing either. The history and particular friendships aside, it's what makes it possible for me, a confessing Christian, to keep fellowship with other Unitarian Univeralists.