If you call this slippin', what was the killing of Carlo in the presence of at least seven people, including Michael, Neri, Tom, Clemenza and some soldiers?
If memory serves me correctly, Michael did NOT issue an order, in front of all these people, to have Carlo killed.
And when Carlo was actually killed, it was in the car as it pulled away without Michael being present.
Michael never uttered a death sentence nor took part or witnessed a killing in the presence of all that you mention.
As for TB's question, I think that at that point Michael's paranoia began to somewhat cloud his judgement. At this point I don't believe that Michael was thinking things out as clearly as he once did or should have been. Traitors and enemies began coming at him from all directions starting with the attempted Tahoe hit, and therefore he could no longer trust anyone.
However, on the flip side of that same coin, I do believe that he also was sending a message to Tom, Neri and Rocco in saying what he did in their presence about wiping out all of his enemies. Letting them know that if he even suspected anyone, including them, or anyone in their regimes, of planning to overthrow him or take him out, he'd wipe them out just for thinking it.
