Possible alternatives

One - Carlo pulls a gun - I assume he had one - and shoots at Mike and Co.
Two - Fredo responds to.Mike in Las Vegas by slamming him against the wall and saying - "Look here kid brother I used to beat the shit out of you when we were kids and.I still can! So just shut your cold mouth and listen ! I wasn't taking sides - I was just trying to smooth things over between you and Moe! Trying to reason with him as the old man said! You just pissed him off. I'm coming back with you to talk to the old man and find out why he turned against me- or was that you ? "