Michael's conversation with Carlo is reminiscent of Vito's with Bonasera. In both cases, the outcome could have more easily been yes or no. But Vito was a master at busting chops in a polite seemingly benign way. Michael had that trait also. He didn't have to get Carlo to confess - his mind was already made up. But it was just part of his personaiity to do so. Just like in the novel when he puts Jules through his paces when Jules tryies to tell Michael that there could be no strings attached. Michael tells him that his string is friendship and Jules can refuse it if he wants to. That wasn't necessary, but Michael seems to revel in tormenting people to some extent.