Despite the danger that Fredo had posed to the family, the issue of morality has to be considered. Michael arranged the murder of his brother despite the fact that he had shunned him after the boathouse conversation. From that point on, what danger did Fredo pose to the family?
Should one murder anyone? Should one murder one's brother? If so, under what circumstance? In this case, to assuage Michael's need for revenge, to punish.
I'm always amazed (and a little disgusted) when people defend Michael's murder of Fredo.
Olivant, you are absolutely right. Fredo posed no continuing threat. The only reasons to kill him were vengeance and punishment.
The murder of Fredo was FFC's way of showing us the complete reduction of Michael from young hero to inhuman monster. And yet people defend this?!