• Michael enlisting in the Marines

The [first time] Fredo took sides against the family

Ola turning up at the Superman club "We never met" for Michael's benefit but making it awkward and uncomfortable for Fredo

True even after Pop had to pull a lot of strings to get him a deferment. Makes it five times Fredo took sides against the family
1. Moe Greene
2. Tahoe shooting
3. Senate hearing
4. withholding information though not vital

Sonny nearly broke his hand. Fredo rubbing it, trying to make sure it was not broken and then sends him off to get him a drink -- go on.

No wonder he was shouting that he was not dumb, smart and I want respect!

Cazale did Fredo like Pacino did Michael though sadly he was not personally nominated, in spite of his stellar performances no doubt doesn’t get enough credit

I couldn't understand why Ola turned up at the Superman club after assuring Fredo Your brother's not going to find out we talked.

The theme of homosexuality is obvious in even the most casual viewing of the film. Fredo's flamboyant clothing in Las Vegas. Fredo allows Moe to slap him. Could Don C. really be "doing the deed" with Mrs. C.? What a chore. I also have suspicions about Michael. Sonny seemed fine. So where could Fredo go in a world of more convincingly heterosexual men. Today it may not have been such an issue.

I think Fredo's sense of style reflected what a gavone he was,more than anything else. He probably thought that he was dressing in a style befitting a gangster of his (imagined) stature.
He dressed like a retiree in Miami trying to look young and "hip"
Also,the reason that Moe slapped him was for "bangin' cocktail waitresses 2 at a time".