I thought that was very interesting and had a great deal of truth to it, if not necessarily on the point I'm addressing, which is how the term is used here, largely, and why.
One particular point in addressing the segregation of public and private morality. To my mind it's more a reflection on a changing context and thinking in relation to general principles of government that we largely failed early in the life of the Republic. On the one hand we recognized the need for an equal standing before the law and the essential equality of man before God. On the other hand we owned people and denied women and others an equal standing before the law or in the exercise of right. Similarly, it was around a hundred years from emancipation to full participation for blacks in our society.
Apologies for not getting back to this sooner. Unfortunately, the time I have to spend posting is sporadic. Sometimes decent time in decent blocks, other times a few minutes here and there. This discussion deserves some serious attention but I fear my inability to address it publicly on a consistent basis hurts the discussion. Having said that, I reiterate what was central to my original response - that liberals (more progressives, I think) tend to give their political viewpoints what might be termed religious status whereas conservatives tend to utilize them but fall short of enshrining them. Maybe more accurately, the conservative (and classical liberal) view(s) tend(s) to see the political ideals as means to an end whereas for the radical/progressive contingent, I think the political values ARE the end. That is, freedom to say and do what they want is their end - they don't see the restraints on behavior as serving another end either. Rather they see them either as repressive (i.e. ALL restraints become tools of repression serving some minority - non-Christian or maybe some non-religious minority designation such as a racial group) or in aid of the end of freedom. Self-government means that and that alone - "I" do what I think is right. It's the enshrinement of the oft repeated phrase found in the book of Judges -
Every man did what was right in his own eyes.
So to your point, I'm trying to thread a needle (at 100 paces, it seems!). "
All men are created equal" is probably a good example of the different approaches outlined. The (radical) left takes that as an absolute statement (which is ironic given the tendency to view the Constitution as something of a living and breathing document that tends to prevail on the left) and an end in itself. But it doesn't take much to realize that equality is a legal convenience meant to achieve an end. Equality is true only in the most fundamental of meanings - equality before God. There is no favoritism with God even though everyone has different gifts, talents, opportunities, positions, predicaments, happenstances etc...And all these are things that are out of the individual's control. So for the purposes of human governance, we have to be equal because none is more elevated in terms of standing before God. That is the ultimate position of government/justice/rule and so to assume it requires (in my mind) the reality of a Creator (which the founding documents also recognize). Not trying to justify the evils of slavery (for example), I also don't think the statement was a prescription for egalitarianism. Roles, social status etc... are not governed by that assumption. Otherwise, that's the way to go from the basic assumption of general equality to the radical definition of equality in all senses. And, thus, we have the lunacy of homosexual marriage and gender "choice". The road from one to the other is not direct, but it is the logical outcome when such statements are given the wrong meaning (and mankind is wanting to cast off basic ideas of common sense - calling good evil and evil good). Slavery, then, is an extreme example of the employer/employee relationship. Not allowing women to vote is an extreme example of unequal roles society sees fit to establish to govern its operation. While we might see these as ridiculous (or worse) the framework of the Constitution laid down the possibility of each of these existing and didn't violate the equality clause. At least as I read it. The choice to hold slaves, for example, was a private judgment for every man to make. I can't understand how someone could do this in light of the biblical injunction. God told Israel that they shouldn't have slaves and referred them to their own 420 year experience. But as a legal right, it was naturally a part of the societal experience. And even one like General Lee agreed that it should be done away with but served a purpose in the short term. Society had to work through the ramifications of this liberty before it could stand against slavery. The law would not free men - only the gospel can do that.
So I return (again) to the progressives. Their gospel is "you are equal (without limit or definition) and free (without regard to morality)". It is in direct opposition to the gospel that sets the captives at liberty - if the Son sets you free, you shall be free indeed. And so I see the progressive position as a religious one - one of secular humanism with an atheistic foundation. Man is his own end. And it's main goal is to unseat God and do away with all those pesky Christians. Either silence them into impotence or literally do away with them. Imprisonment and economic destruction is a current tool but I do believe that the day is coming when (somehow) the moral restraint God now holds on men is totally removed and progressives will have (rather, give themselves) free reign to kill whoever gets in their way. I also think that's why they find such kindred spirits in Islam (but that's another topic altogether).
With the church, for generations laws which favored both one religion and in some cases a particular form of it were on the books in many states and echoed in the larger federal government. Those laws often promoted the idea that many fled Europe to avoid, a state sanctioned church, if created de facto. It wasn't really addressed or much of an issue because so many of the early peoples of our nation shared the same faith and settled into communities that reflected their particular brand of it. Generations of people were born and died in those same communities. The industrial awakening of America changed that. It brought a migratory trend among the people, began to change the ease and assumption of those established communities as people entered into them with different practices and ideas. Eventually it challenged it to the point where what had been an easy and invited yoke became an obvious problem.
I think the "one religion" concept is very powerful. That is, order and (some form of) justice can easily be maintained in a homogeneous society. That homogeneity is religious far more than it is anything else (racial etc...though I've sometimes wondered if Acts 17:26 at least supports the idea of national sovereignty being a biblical necessity). Religious belief is a tie that binds very deeply and with great strength. And it is what really, in the end, is (again, my opinion) the primary factor in the formation of what we call culture. I think - in a superficial sense, anyway - that is why the Jews have been so persecuted over the ages. Their idea of culture has remained in tact in spite of great....stress (to put it mildly). They have maintained a culture that has religion at its very core. There are all sorts of different Jews, but their cultural distinctives are religious at the heart of it all. That isn't to say that they are religiously correct, but that their unity and cultural strength is owing largely to their religious foundation. Islam has this to a great degree as well. Christianity - the popular kind - has been so watered down that its cultural impact is all but gone. Again - that only goes to the unity and stress placed on belief - not the rightness or wrongness of core beliefs. I believe that a Christianity tenaciously held is unstoppable and will (has been - see 17th/18th century England/North America and Wesley/Whitefield) revolutionize any people.
In terms of Congress not making any law respecting religion, that's a debate I don't know that I'm fully equipped to even define properly. I've heard it said that it meant that it was understood that Christianity was the accepted religious foundation and that denominations were in view when "religion" was used. But it also could be taken at face value and simply means that a person's private observance of religion is not a matter of concern for the government - so long as it doesn't impede his ability to keep the law of the land (which is based on English Common Law which is based broadly on scripture). Multiculturalism has opened Pandora's Box and there is little chance of closing it again. And so while it may not be popular, there is a sense where we are getting a glimpse of what Ezekiel saw in the temple - all the foreign gods drawing Israel away from the One True God. But again, as I said above, the solution isn't necessarily immigration - it's spiritual.
Well, I think I've rambled on enough. I had wanted to make my initial responses a little more substantive than I actually did - and now with the time to do so, I think I've shown why I was a little hesitant to respond. Too many directions to go - many of which may not be true to the OP enough to be maintained in this thread (and enough to give any reader mental whiplash).
Respond as you will - to one point, some of them, all of them or even none of them. I'm sure the way I have it on digital paper, it isn't nearly as clear as it is in my head....