And if you look closely at that scene, Barzini gives himself away. He, not Vito, sits at the head of the table. He, not Vito, takes the lead in the discussions--and he jumps the gun on Vito by declaring: "Then it is settled. The traffic in drugs is allowed, and Don Corleone will give it protection in the East. And there will be the peace."
This is not really so implicating, is it? Vito opens his own remarks by thanking Don Barzini for helping Vito to organize the meeting. Vito's a party to the dispute, and so can't chair the meeting. It could actually be that Vito learns more from the silence of Cuneo and Stracchi than from anything Barzini says.
