Ask him for further reading, so that you can follow the logic yourself. Truth is, he's right on this point, and you will be a more credible conservative in general if you don't close your ears to evidence and go la-la-la when he makes a logical case.
You, too, almost surely have logical arguments for some points where he's stuck in denial. People are like that, picking and choosing when they'll use their head and when they'll just go with team-think. Your best way to budge him off that stance is to budge yourself in this instance, where he's right and you're wrong.