I don't think the point of prison is to change your views (the system doesn't care what your views are). It's to make you less likely to re-offend and the vast majority of people to not offend at all. I would guess that there are lots of people with radical views who never act on them exactly because they are afraid of the legal consequences (e.g. prison). This means the system has worked on them.
EDIT: Not that I'm defending any particular prison system or making a moral statement here. In many countries the prison system is horrible and probably not even very optimal at preventing offences. It's just that in my mind the prison has one main purpose; to act as a deterrent for crime, and most of the time, for most of the population, it somewhat works for that purpose.
EDIT: Not that I'm defending any particular prison system or making a moral statement here. In many countries the prison system is horrible and probably not even very optimal at preventing offences. It's just that in my mind the prison has one main purpose; to act as a deterrent for crime, and most of the time, for most of the population, it somewhat works for that purpose.