I think that we must take the whole scene and the whole conversation into consideration here.



I think that his lines to Moe..."My credit good enough to buy you out?"..."Your casino loses money" ....are abrupt lines that intentionally insinuate that Moe is skimming. And Michael wants Moe to know that he suspects him of skimming. It was his way of pissing off Moe without directly accusing him of skimming. It was Michael's way of getting Moe to bring up the skimming himself. And then with his "you're unlucky" response along with that 'that's all I'm saying' look on his face, Mike makes Moe Green look, in front of everyone else, like he's guilty of some wrong doing. Makes other sitting in that room say to themselves "Why would he bring up the term skimming? Michael never used that term, he did. So maybe he is skimming." And what does Moe do in front of everyone in that room? He attacks the Corleones, he reveals that he has been talking to Barzini. Moe was head-strong, talking loud, saying stupid things. And Michael knew how he was. A cunning move by Michael to make Moe look like the bad guy that had to go.