Regarding Michael, obviously it had a personal effect on him when his father was almost killed. Business-more so, Personal-yes
The turk had to be killed or the Corleones would have to nagotiate with him which isnt what a Corleone does. In business, he had more options, but peronally, he wasnt going to let the attempt pass.
So, that night at the restraunt, he was settling an arguement with an associate and an enemy.