I was just about to make this post. Glad I searched for it.
I say no. I understand why Michael did it, but...it was Fredo. Fredo, for fukk's sake. If it was Sonny or maybe even Tom, I would've understood. Those men were threats. But Fredo was such a fukk-up that he didn't even realize that he was setting his brother up to be killed!
At no time did Michael have anything to fear from Fredo. Michael killed Fredo on GP - understandable, but that was his brother. His stupid, weak, punk of a brother. Banish him, cut him off, leave him to fend for himself. But Fredo was not a threat. He shouldn't have been killed - and the fact that Fredo's death tortured Michael for the rest of his life proved that.