You propose to get an unbeliever to accept what the Bible ("just a book") says about what "real people" should do with their lives. Why do you think we've lost and will continue to lose? If you don't care what the Bible says on the subject, then any such counterargument is irrelevant.
The words from Kipling
in Gods of the Copybook Headings still apply
Natural Law instructs us well on consequences
...When the Cambrian measures were forming, They promised perpetual peace.
They swore, if we gave them our weapons, that the wars of the tribes would cease.
But when we disarmed They sold us and delivered us bound to our foe,
And the Gods of the Copybook Headings said: “Stick to the Devil you know.”
...On the first Feminian Sandstones we were promised the Fuller Life
(Which started by loving our neighbour and ended by loving his wife)
Till our women had no more children and the men lost reason and faith,
And the Gods of the Copybook Headings said: “The Wages of Sin is Death.”
...In the Carboniferous Epoch we were promised abundance for all,
By robbing selected Peter to pay for collective Paul;
But, though we had plenty of money, there was nothing our money could buy,
And the Gods of the Copybook Headings said: “If you don't work you die.”