This is the world of organized crime.

You do not get a "pass" for having been deceived. You are not judged on having been deceived, you are judged on your behavior. Frankie was about to testify against his Don, which if he had gone through with it would've sent Michael to prison. Once coerced out of that, he was of no use to anyone. Not the Feds, not the Corleone Family. Wife & daughter don't count...but they at least get taken care of.

Yes, Frankie was deceived. As a result, he turned traitor. He deserved sympathy...but he didNOT deserve a "pass".