Communist propaganda and downed U.S. aircraft? That’s entertaining. Vietnamese communists had their first big PR coup during the Tet offensive of 1968, when CBS’ Walter Cronkite ignored the decisive U.S. military victory and told America the war was unwinnable. Three and a half decades later, here comes CBS again, allowing an entertainment show to participate in a bit of old-fashioned communist propaganda. The March 17 episode of “The Amazing Race” featured its usual routine; teams travelling to different countries and completing tasks in a race to reach the finish line. These tasks typically involve learning about another culture. However, in...