Morality was not handed down as a social edict from God. Morality is the successful result of millenia worth of interaction between humans. What works survives and what doesn't dies off. Christians are fond of saying that the US is a Christian country and also the most successful country in the world. They point to America's morality as being the reason behind the US's success.
I do believe that the basic morality of the US is excellent (respect for life and property with freedom in as much as that freedom does not infringe on the life, property and freedom of other people.) The efficacy of this belief can be supported by the evidence of a successful and prosperous civilization. This morality then becomes the individual morality of its citizens. For example: Tolerance is considered to be a virtue in the US even though intolerance is standard in Muslim and Christian theocracies.
Was the Aztec theocracy wrong? Any human (or animal for that matter) will try to avoid being killed, having its property (food) stolen and imprisoned. The Aztec theory of government would require the subjugation of its populace through fear, intimidation and religion. This actually worked for awhile yet a different civilization with a superior government philosophy outcompeted and destroyed it. Our world is made up of a host of competing moralities and governments - eventually the government with the best morality and political philosophy will win in the long run.
Let's say however that the Aztec theory actually worked and the subjugation of a civilization along with bloody human sacrifice would lead to great technological advancement and prosperity. If that happened then who could argue that the Aztecs were wrong? We would be looking back at the overly free experiment of the USA and realize that humans must be subjugated to be productive.
Let's look at Europe. Europe is adopting a socialist philosophy - more in line with Jesus' teachings than the USA. This philosophy moves in the opposite direction of an Aztec ideology. Tolerance, diversity and redistribution of wealth at an almost religious level seems more moral YET the extremist tolerance/diversity philosophy is allowing that civilization to fall before the invasion of a hostile Muslim force which will eventually rise up against their hosts. This tells us (without any holy writings) that tolerance is a virtue but only to a point. Socialism allows that less people go hungry or have medical bills that cannot be paid - however Socialism destroys the productivity of a people and drives the economy of the countries into the ground. Everyone trades on the US' NYSE but few people bother with Europe's minor stock exchanges - socialist governments produce much less profit than a capitalist government. When the Pilgrims landed they felt that it was moral to create communes (like in Acts 4) so no one would starve - but they quickly discovered that without incentive people didn't work. This meant that the Pilgrims disbanded the ideology and went forward with a market system. What works drives morality - not the other way around.
Christians have to realize that they have abandoned much of their Bible oriented morality and chosen secular morality instead. Is owning property good? Well the early Christians would chide you for not selling all your property and giving it to the collective so no one would be poor. Problem is... this model has never worked so Christians generally don't follow it - they consider capitalism to be 'good'.
Let's read the following passage from Deuteronomy... Would any Jew or Christian do this today? Is there anything in the New Testament that tells us that we should no longer follow the Deuteronomical codes?
13:6 If thy brother, the son of thy mother, or thy son, or thy daughter, or the wife of thy bosom, or thy friend, which is as thine own soul, entice thee secretly, saying, Let us go and serve other gods, which thou hast not known, thou, nor thy fathers; 3:7 Namely, of the gods of the people which are round about you, nigh unto thee, or far off from thee, from the one end of the earth even unto the other end of the earth; 13:8 Thou shalt not consent unto him, nor hearken unto him; neither shall thine eye pity him, neither shalt thou spare, neither shalt thou conceal him: 13:9 But thou shalt surely kill him; thine hand shall be first upon him to put him to death, and afterwards the hand of all the people. 13:10 And thou shalt stone him with stones, that he die; because he hath sought to thrust thee away from the LORD thy God, which brought thee out of the land of Egypt, from the house of bondage.
See - no Christian or Jew today would KILL a proselytizing friend. That civilization model (rabid, homicidal intolerance) didn't work so that behavior is now considered a vice instead of a virtue.
I'm happy to say that today's Jew or Judeo Christian in SPITE of the Old Testament:
Does not wage wars of aggression.
Feels that slavery is wrong.
Tolerates other political and religious views.
Charges interest on borrowed money.
Has contact with menstruating women.
Allows people to work on the Sabbath without killing them.
I'm happy to say that today's Christian in SPITE of the New Testament:
Does not hate capitalism.
Gets a job.
Defends himself and his family.
What is funny is that Christians HAVE to live a life completely opposite of Jesus to run a reasonable society. Christians (unlike Jesus) arm themselves, get jobs, get married, kick social parasites to the curb instead of giving them their coats, become involved in society, save money and try to put enough away so they can leave something to their children Jesus - like Mao, Marx etc was a philosophical failure.
It's simple trial and error - as humans we keep what works and discard what doesn't... easy!