Again it is important how you characterize a traitor. In my eyes a traitor is someone who consciously sides with another family to get your boss/superior killed. For Example Carlo was a traitor because he wanted Sonny dead after the beating AND he thought with sonny gone he would finally move up in the family. Tessio even though he was loyal to Vito and did like Mike he set up Mike to be killed to start his own family. Fredo on the other hand was different. Its clear he was misled and used. Was he weak,stupid,resentful? Absolutely. But it clear his goal in his mind was that he was doing something on his own but helping the family.....he didnt want mike harmed, he didnt even want him out as boss.
This brings up an interesting point: What did Fredo really believe and want? Did he really think that no harm would befall Michael when he told Roth the layout of the house? Did he think that, if he helped close the deal with Roth, that Michael and the rest of the Family would be pleased and give him a more substantial role? Maybe make him the boss, to rectify the mistake of him getting passed over.
I think one of the themes of the Trilogy (and GFII in particular) is people lying to themselves.
Michael believes he can become legitimate while running the nation's top Mafia Family.
Kay tells herself that the Family will be legitimate within 5 years.
Roth thinks he can rule his empire forever.
And Fredo tells himself that he can take sides against the Family and somehow end up more powerful and respected.
They were all wrong and they were all doomed to suffer a violent death or the violent death of those closest to them.
There really no evidence that Fredos goal is to be the boss despite what he said about being passed over. Its pretty clear all he wanted was some respect as a mobster. He was well liked but mostly out of pity. I think some are still trying to convince us that Fredo was vindictive and treacherous like carlo and tessio. The film makes it clear that its not the case. Part 3 is about how the choice to kill Fredo was evil and senseless
