The entire post is good but I want to highlight something that I find myself frequently arguing about on this board:
Alistair MacIntyre's entire thesis is essentially that morality and ethics are socially derived and therefore not universal but rather irrational and normative to the community that produced them.
I wholeheartedly agree with the above and find myself more frequently abandoning arguments these days because the other person's position is predicated on the idea of a universal set of morals and ethics that frankly never existed in the 1st place.
As for the larger point in the OP, I think this is how it has always been and why we have a representative democracy instead of a direct one. On a national scale, the community morals and ethics are constantly in flux and the rational arguments that are derived them are constantly in flux as well.
When you look in a history book and they can cover 50 years of social, moral and ethical change in 2-3 pages, it's easy to think that these things happen quickly and painlessly. In reality, these changes are often long and drawn out with a majority position rarely apparent to the people living through the time period.
I think our current era is going through a significant reconsideration of our social, moral and ethical positions. It's driven by changes in demographics and changes in technology. The demographic changes mean that new S/M/E positions are entering the public discussion with greater weight. The technological changes mean S/M/E considerations must be filtered through a new lens.
The 2nd Amendment is an easy example. When the S/M/E arguments behind the 2nd Amendment were being considered the technological capabilities of armaments, both for the nation and the individual, were very different from what they are now. As destructive capability increased, it's natural that the 2nd Amendment's S/M/E considerations be revisited.
In the end, I subscribe to a simple philosophy. Society shapes itself then it shapes government. Accordingly, there can never be a permanently defensible moral or ethical argument in politics. And to this end, the Constitution takes on greater significance. It acts as a bulwark against changing moral and ethical arguments significantly dictating the boundaries of the government that must govern numerous competing S/M/E positions.