This is one of those things that J.W's dismiss as the experts, Scientists, Archaeologists etc simply getting it wrong, because the bible says different.
We should use Black Sheep's method, ask them what is wrong with the expert opinion on all these sites and finds , and get them to explain, don't let them waffle something about "Dodgy carbon dating" without backing up what they say.
It is an important issue, because once you get them to see that a literal interpretation of the Bible is impossible, and therfore it is all about interpretation, they can begin to see that they are listening to the thoughts of men.