a true fact

We've met a few people, all from the Battlefords, and none of them related to us, who use the expression "That's a true fact!"
Seriously, though, is there such a thing as solid, universal truth. I believe there is, of course, but can it be proven or indicated by experience?
I read a book years ago called Peace Child - I don't remember the name of the author - about a missionary couple who went to Papua New Guinea to evangelize a tribe of cannibals and head-hunters. When they first told the story of the Gospel, all the men of the tribe cheered when they heard the part about Judas' betrayal. As it turned out they loved treachery - thought it was the greatest thing when they could stab someone in the back after a peace treaty. That stymied the missionaries temporarily, until one day they witnessed a ceremony they did not at first understand. The chief of the one tribe gave his firstborn son to the chief of the neighbouring tribe. When the pastor asked what it meant, he was told that this was the one act that could put an end to all treachery between the two tribes. Then he was able to teach them that Jesus is the Peace Child given by the Father to the world to make it possible for us to be at peace with the Father.
A friend asked me recently if there is universal truth, if those cannibalistic head-hunting people had any idea that the way they had been living was wrong. I wouldn't know for sure, of course, but I wonder if their former treachery would have been half so "fun" if they hadn't had some realization that it wasn't right.
Are there moral absolutes? I think, like C.S. Lewis, that even people who believe there are no moral absolutes get mighty offended if you try to steal their watch. They also have some sense that if they share their outrage with the world, most people will side with them. Moreover they sleep fairly well at night, knowing that the sweet elderly ladies next door probably won't murder them in their sleep.
Don't we all assume a basic moral code exists?