I can see that argument, but I guess I just don't think I'd personally make that decision in the case of lengthy imprisonment. It's probably a laudable one, but my interest in not spending decades in a claustrophobic situation without freedom, subject to what seem like fairly frightening possibilities (high prevalence of prison rape, etc.) would likely outweigh my desire to live an inspiring life as a prison activist. I think the fact that you can't change your mind later is what frightens me about it in particular. If, a few years in, it's so horrible that I really would rather be dead, it's too late to do anything about it at that point; once you go in, there really is no escape.

In just about any other case I would agree with your assessment of the choice, though. Most seemingly hopeless situations are really not hopeless.