I'm on the "it was business" train on the murders.

Also I do believe Sonny would have either shot or beaten Carlo to death if he would have gotten to him.

In mafia code generally you have to "break a rule" to get hit, and to most they consider that "justified" to commit murder and it makes it o.k. Of course we all know most rules are twisted during beefs to make it justified as well. The rules are only followed when its time to clip someone.