I am a member of the United Methodist denomination.
Having spent some 20 years of my life as an Army Chaplain, I have run across all types of denominations. Religion in the military is really no different than religion in America. The Army gets a cross-section of just about the entire US population in almost every category. Religion is no different.
I can vouch after years of experience that there really are those who are not part of an organized denomination. Generally, they do not accept hierarchies and are organized as independent, local churches. They owe no allegiance to any higher body.
We regularly used the expression “non-denominational” to describe folks from this type of religious confession/affiliation.
In that they do have these distinctives in common, it seems only fair that they, too, be able to caucus to discuss those items common to Christian groups that eschew hierarchical or organizational ties.
Let me recommend that Free Republic discuss this with the Religion Moderator before they make a hard and fast rule in this regard that discriminates against what truly is a common, separate type of religious expression in our country.
"Non-denominational" is a valid category for caucuses, etc.