There's a number of (admittedly trivial/minor) points that I would disagree with the Rabbi on, but when they start off as early as this, I have trouble accepting his authority with the greater message. Had footnotes been provided along the way (perhaps he's citing the Talmud?), it would have helped his case.
What always has amazed me in the history of the Givon battle is how God used the humility of the Givonites in bowing before the Israelite God to call together the strong confederation of southern city kings to do battle. Because of the Givonites, Israel did not have to fight prolonged wars with the southern kings, they were defeated in a day and all Israel had to do was mop up after. In a short time they had taken Jericho, Ai, Givon and the southern district with the exception of Jerusalem. What a confidence builder in God's promise to go before.
God left them to die in the wilderness because they didn't see what great things were being offered them.
Joshua & Caleb saw.
They were content to lead of dead-end life of wandering in a wilderness or being a slave.
Best to give that sort their own lead and let them die off.