Sometimes I think we read too much into some scenes. It's pretty simple. Michael was outraged that someone fired at least a clip of bullets into his bedroom and nearly killed his wife.
Maybe he had more of Sonny in him than we knew.
"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"
