Checking the links on the GodandScience website, and under "Authenticity of the Bible" going to "Archaeology and the Bible" then "Is the Bible true? Extraordinary insights from archaeology and history by Jeffrey L. Sheler"....
I find the following:
FLIGHT FROM EGYPT
The dramatic story of the Exodus -- of God delivering Moses and the Israelite people from Egyptian bondage and leading them to the Promised Land of Canaan -- has been called the "central proclamation of the Hebrew Bible." Yet archaeologists have found no direct evidence to corroborate the biblical story. Inscriptions from ancient Egypt contain no mention of Hebrew slaves, of the plagues that the Bible says preceded their release, or of the destruction of the pharaoh's army during the Israelites' miraculous crossing of the Red Sea. No physical trace has been found of the Israelites' 40-year nomadic sojourn in the Sinai wilderness. There is not even any indication, outside of the Bible, that Moses existed.
Still, as with the patriarch narratives, many scholars argue that a lack of direct evidence is insufficient reason to deny that the Exodus actually happened. Nahum Sarna, professor emeritus of biblical studies at Brandeis University, argues that the Exodus story -- tracing, as it does, a nation's origins to slavery and oppression -- "cannot possibly be fictional. No nation would be likely to invent for itself . . . an inglorious and inconvenient tradition of this nature," unless it had an authentic core. "If you're making up history," adds Richard Elliott Friedman, professor at the University of California-San Diego, "it's that you were descended from gods or kings, not from slaves."
Indeed, the absence of direct material evidence of an Israelite sojourn in Egypt is not as surprising, or as damaging to the Bible's credibility, as it first might seem. What type of material evidence, after all, would one expect to find that could corroborate the biblical story? "Slaves, serfs, and nomads leave few traces in the archaeological record," notes University of Arizona archaeologist William Dever.
The dating of the Exodus also has long been a source of controversy. The book of 1 Kings 6:1 gives what appears to be a clear historical marker for the end of the Israelite sojourn in Egypt: "In the 480th year after the Israelites came out of the land of Egypt, in the fourth year of Solomon's reign over Israel, in the month of Ziv, which is the second month, he began to build the house of the Lord." Biblical historians generally agree that Solomon, the son and successor of David came to the throne in about 962 B.C. If so, then the Exodus would have occurred in about 1438 B.C., based on the chronology of the 1 Kings passage.
That date does not fit with other biblical texts or with what is known of ancient Egyptian history. But the flaw is far from fatal. Sarna and others argue that the time span cited in 1 Kings -- 480 years -- should not be taken literally. "It is 12 generations of 40 years each," notes Sarna; 40 being "a rather conventional figure in the Bible," frequently used to connote a long period of time. Viewing the 1 Kings chronology in that light -- as primarily a theological statement rather than as "pure" history in the modern sense -- the Exodus can be placed in the 13th century, in the days of Ramses II, where it finds strong circumstantial support in the archaeological record.
http://www.uhcg.org/news/is-bible-true.html
Now, this may not be all that you would like to hear for the sake of your response, KMart, but it is still important to know as much as possible, even if there is a paucity of proof available. However, it does give some suggestions for how to approach the issue. It may be that your questioner has read this piece of writing too!
If that quote came from a dubious website, then it would be surprising that GodandScience supports it's mention on their own website.
KMart, I like your use of Chesterton's argument, and as Bizzt says, have the other person substantiate his claim as you are entitled to know what truth there may (or may not) be in it.
Bizzt, you mention documents regarding Moses being a real person. I'm another who likes to know where to find whatever is useful in answering questions posed by non-believers, so if you can provide any links, I'd be interested to read more.