Tony arches an eyebrow and then shakes his head. "You don't blame a weapon," he says. "You blame the person that handled the weapon." And he didn't know who that was. It could have been anyone. SHIELD was so infiltrated that it's impossible to know who was giving orders to whom.

What he does know is that Bucky was command oriented.

He was the gun, the missile, the bomb.

So while you might not blame the weapon...you can turn it on it's masters. Tony's smile fades. "Take a nap. I'll sober up. I'll get you fixed."