He's actually asking you to laugh at him, so go ahead. Besides, maybe if you laugh, he'll back off.
His take on the Vikings sounds fairly bogus. They fought plenty of people with advanced weapons. They invaded France periodically for a couple of hundred years until the French kings bought them off by giving them the peninsula of Normandy to settle in. (Yep, the Norman invaders who conquered England in 1066 were actually descendents of Vikings).
http://www.luth.se/luth/present/swed...king_age1.html