I have this same debate with a liberal historian who clings to the mantra that whatever the US does makes things worse in the world. Hanson's recitation of what the world would be like without US global military and political engagement would not be conceded or acknowledged by this PhD who still credits Gorby for the demise of the Soviet Union more so than Reagan. Likewise, the issue of free-markets and the use of capitalism as a weapon of freedom is never conceded by these same pro-Socialism folks who find allies among the Walmart and outsourcing haters from both parties.
That guy is not a liberal; he is a NeoLib.
Use that, it drives them nuts.