"Exile would have been sufficient. The murder was strictly personal and cannot be justified by business/security concerns."

Exile would not have been sufficient; Fredo was a threat as long as he remained alive. Maybe not in the immediate future, but somewhere, somehow down the line, maybe years, was the possibility of another betrayal (this one w/ Roth was not the first - only the most damaging).

The murder wasn't personal...it was business. Had Michael allowed Fredo to live ONLY because they were brothers (for there would have been no other reason), then THAT would've been 'personal'. The only personal aspect was the compassion Michael showed his mother in not permitting her to lose another son.

"Killing your own brother is rather like dropping the atomic bomb ... even if they felt their brother deserved to be killed they couldn't do it without deeply mixed feelings and deep sadness that the whole situation came about in the first place."

And what is conspiring against your own brother with a known rival, even if to smooth negotiations? Thereby knowingly or unknowingly, nearly causing his death and the downfall of possibly the entire Corleone Empire? Is that akin to dropping a bomb?

People seem to love to forget the seriousness of what Fredo did. Michael Corleone did not simply wake up one day and decide to kill his brother.

I believe Michael DID have mixed feelings and sadness that it all came about...however he knew what had to be done. Also...that statement that Fredo was nothing to him, neither a brother nor a friend...should be taken very seriously.

In short ...I agree with Michael's decision.

Fredo HAD to go.