Never said that morality was invented in the Old Testament or New. . .
We can give credit to the Greeks for upgrading of Christianity; and in turn, Vedic scriptures et al - we can go 'round the world and back again' for earlier contributions on moral structure and behaviors.
But the Ten Commandments more immediately, reflect the Deist/Judeo/Christian beginnings of our Country. They stand as a moral reminder; a moral base for our 'laws' that distinguish good behaviors from unacceptable.
And in that context, they should be recognized and honored.
Now about rediculous. . .moral laws as the result of 'two people deciding it is better/easier to work together than not, ie common sense?'
. . .no, think it far more simple than that.