...Santino had a job to do, and that job was to win, goddamn it!
True...but take the 'Pop had Genco, look what I got..." argument, where Tom pointed out the Family couldn't do any business. Sonny's response was, 'Neither can they...!" Which indicates there was a bit more than merely winning on his mind.
...Sure Santino beat up Carlo! Who wouldn't? The guy was a skeezer, a scumbag...
Sure, and frankly Carlo deserved the beating. But considering the circumstances...a more rational 'acting Don' might've not been so public and severe about it. Sonny was not just any protective older brother.
...His one true fault is that he can't keep his donkey in his pants. But that doesn't make him a psychopath. A bad husband, maybe.
And...in the words of his own father, 'A bad Don...rest in peace.'