Sure, I think it's wonderful that religion promotes these morals that teach humans to not be dicks to each other. Despite its neutrality, I like this comment more than the others in this thread.
However, is it required that we establish a religion before establishing the laws? Or is there another answer? Could it be that we possibly knew consciously that horrible crimes like theft, murder, etc. was already bad and we created the laws to establish Justice? Because while we knew that murder and theft is terrible, we would still take revenge on those that wronged us. So that's what the laws were set in place, to do the justice for that wronged citizen.
I like that you're more rational than what I had to deal with. Now the difference in the Norse Vikings is that they plundered completely different countries. They didn't squabble with each other. Their own established laws prevented that, and they were content with it. Did they need religion to establish these laws? No, but they did in fact use the Norse Gods as witnesses to court hearings to deter people from lieing. But they did not use the Norse Gods to create their laws. There was order in their civilization, and there was no need for someone to say "these laws are here because of the Norse Gods" to do it. Because they made it with their own hands.
The Constitution did not directly get the laws from the Bible, rather the Quakers who lived up North created their laws from the Bible, which in turn was used as a template for the Constitution, as it contained several of the first Amendments, like Freedom of Religion, in their codes. Several founders of the constitution weren't explicitly religious, which is why the USA was not founded as a Christian nation, rather they felt the need for all religions to be practiced and that they made sure that no law for or against religion was passed (First Amendment).
Am I making any sense here? I'm trying to show that this in fact can be done, secularly and with Order.