Interesting thread! I'll admit that I'm probably one of a minority of UU's who are almost fanatical in my faith, and have been for over 30 years now. (After all, how many people do you know who actually go to a public library to "find a religion"...literally investing days, studying and comparing the various religions of the world--large and small--before finally narrowing my choices and selecting UU as the one which I could support "heart and soul," without reservation?) While I would not by any means want to suggest that "everything UU" is as dead-serious as that, I'm quick to suggest (or contend) that to me at least some of it is, and that what we have to offer society is both distinctive and worth sharing.
I thought I needed to offer you that background info to explain why, when I decided to launch some online discussion groups for UU's, two of them were deliberately intended for the "sinking of our teeth into deeper issues"---such as the one covered here, in this thread. (Those groups are actually aimed at "UU-style evangelism" and all sorts of issues relating to UU growth, or lack thereof). Anyway, this is a conversation that I always welcome, as long as its tone is respectful and courteous.
In one of those groups, I posed the question "Is there a liberal protocol" (in religion)? I suggested that yes, there is one: It goes largely unspoken and is not as "dogmatically carved as stone" as most orthodoxy faiths, of course...but it still does exist. It's a protocol composed mostly of shared attitudes and methodology--and is therefore defined mostly by adjectives more than nouns--but it's still real and substatial, and even carries with it certain (at least implied) mutual expectations.
One of our expectations of one another is that we at least will try to use our precious freedoms wisely...an expectation of discipline (self-imposed). This goes beyond the shallow belief that "we can believe anything we want to." We also expect from one another at least an attempt at being honest...at integrity, or continuity in our beliefs, and between our beliefs and the lives we live. (One pre-merger Unitarian minister even once contended that a "dishonest Unitarian is a contradiction in terms.) And, flowing from such a "true colors" approach to religion also (inevitably) comes honest admissions of our human limitations ...including limits to "what we really know" as "absolute Truth." (In other words, humility, tolerance and openness--qualities that are all-too-often lacking in the realm of religion--are actually hard-wired into our approach to religion.) So...to make a long story/essay/sermon short, I'd agree with those who feel that there is more to UU than a pluralistic collection of other faiths. What we have is our own distinctive tradition and legacy in religion that is every bit as hard-won, legitimate and valid as any of the others. It just seems to me that what we share together--as kindred spirits of liberal faith-- goes a little deeper than just a "pluralistic buffet" of religious beliefs and rituals. It asks a bit more of us than just to be there, in that lunch-line, at that cafeteria of freedom, reason and tolerance.
I'm not sure that I've articulated that very well, but maybe it makes sense. I'd certainly be interested in your own take on this!