"Stallman posited that it would have been RIGHT for Minsky to have sex with her, and he couldn't have known she was underage"
He said no such thing. Luckily, even when the controversy first came up, Vice made a full copy of the email chain. He sees no reason to doubt initial reports about Minsky's supposed encounter and simply errs on the side of caution; Giuffre had been coerced (by Epstein) but it was unclear what role Minsky would have had in harming Giuffre. He seeks information about the deposition to inform himself better of the facts of the case. To me, this is a reasonable amount of nuance for a still-developing story (at the time).
People are falling into a predictably emotional trap now as they did two years ago. I urge everyone to read things closely for themselves as the primary sources are mainly digital and can be freely accessed by anyone.