While I think the "solitary confinement in Guantanamo" assumption is probably off-base, certainly he'd be in a tough situation somewhere, and he probably did make the right choice. I definitely wouldn't have had anywhere near the courage he has shown in his whistleblowing, let alone the courage it would take to face the punishment.
Nonetheless, I'll expand on what I meant by "popular"; in the mainstream his flight is seen as evidence of guilt, and the particular countries to which he fled cast even more of a shadow on his intentions. Lots of people I've talked to think he must be an enemy because he fled. Martyrdom is always terrible for the martyr but often better for the martyr's ideology than the alternative. You're definitely right that he's having a continued impact on the discussion, and perhaps that does make his exile a net positive for his ideology. But the people I know who think he's a traitor who betrayed his country before seeking asylum with its enemies don't tend to listen to what he has to say.
Nonetheless, I'll expand on what I meant by "popular"; in the mainstream his flight is seen as evidence of guilt, and the particular countries to which he fled cast even more of a shadow on his intentions. Lots of people I've talked to think he must be an enemy because he fled. Martyrdom is always terrible for the martyr but often better for the martyr's ideology than the alternative. You're definitely right that he's having a continued impact on the discussion, and perhaps that does make his exile a net positive for his ideology. But the people I know who think he's a traitor who betrayed his country before seeking asylum with its enemies don't tend to listen to what he has to say.