Yeah, I'm not seeing a real issue of hypocrisy here. He's attempting to buy demiled military equipment, not guns. If he was buying collectable, functioning machine guns or something, yeah. But he's not. The guy's definitely a douche and elitist for donating that much money to gun control but it's his money.
If you had the money you could go out and buy the same things without a background check because it's not a firearm.