Sorry but Flynn, Manafort, and Stone should never have spoken to the thugs in the first place - at least without competent legal representation.
Flynn had no idea he was being questioned about an investigation. He was screwed from the get go.
Forget who I heard say it, but stuff (texts, maybe) was uncovered between/among Flynn's interrogators, before their meeting with him, discussing how to put and keep him at ease, so he would just presume the "discussion" was friendly-to-friendly instead of a plot to frame him.
Hanging. They need hanging.