While I don't know how in the hell four MG42's is somehow a decent substitute for a .50 BMG anti-aircraft rig, that NRA commentary is spot on.
It's not that it is a good sub, since 4 M2s > 4 MG42s. As he told the guy buying it, it was a $$$$$ thing with the ginormous cost of the .50 ammo, and the savings of going with the mg42.