I really fail to imagine how a society can arrive at a universal ethical standard without writing a couple ideas down here and there. You're asking for a utopian society of mind readers, which hits me as just a touch unreasonable.
I was about to say, "we can at least agree that murder is bad", but I'm not sure that's even the case, given that it seems like some people would think it's ok to murder their political opponents if given the chance.
When I grew up, which was not long ago, we viewed America as that curiously Christian country of the West. Everyone else was very secular, but those American? They're all Christians, they're crazily religious.
Maybe this has become less true over the last decade or so, but I think that you'll find that the percentage of Americans that describe themselves as Christian is still very high. It seems that there is a pretty universal ethical standard at the most fundamental level. It just turns out that, like all things in life, people disagree about how to translate broad, abstract moral claims into concrete policies. You might agree on a 'separation of church and state' or 'free speech' but that doesn't mean you agree on what that means in practice. Does it mean that public officials shouldn't be allowed to display religious symbols, like it does in France? Does it mean that Islamic headscarves on women and crucifix necklaces are banned in schools? Does the UK have separate religion and state? Certainly its political process is less influenced by religious voting blocs than America's. But its head of state is Supreme Governor of the Church of England. These things are complicated.
Damn straight!
One approach I’ve tried in the past is to explain that the people start with all rights, the government starts with zero privileges, and the explicit examples codified in the Constitution are simply bare minimum examples of lines that shall never be crossed.
The militia prefatory clause of the 2nd amendment is a great example of this as explained by Scalia in Heller. It’s not that that the right to bear arms is solely for members of a militia. It’s simply one example of how the individual freedom (that innately exists!) may be exercised.
an inherent right to defend ones self includes ability to equip to do so effectively
People assert they have all sorts of rights all the time. Most of them conflict with other rights that other people assert exist, and even other rights that they themselves assert exist. What do we do about this?
I actually think 'rights' legislation is pretty stupid. It's a lot easier to write an Act that says 'Every one has the right to a free, public and comprehensive secular education' than it is to write an Act that provides a free, public and comprehensive secular education system. The latter requires sorting out what all of those things actually mean in practice. What level of education do you provide for free? What level of choice do people have about their children's education, vs the view that as a society we should protect children from the 'bad' decisions of their parents? That also means protecting them from their parents' good decisions. Are we okay with that? What does it mean for education to be secular. Are they allowed to learn about religion? Are they allowed to close the school at lunchtime and teach religion in the afternoon, unofficially, as often happens? Concrete systems are much more important and much more effective than any abstract statement of 'rights'.