I loved the books as much as anyone, but Azkaban struck me as utter barbarism even then. You're telling me that prisoners, regardless of what they were actually sentenced for, get psychologically tortured through the magical induction of deep despair until they develop a form of dementia? And this happens whether you're a murderous dark wizard or you do a bit of magical petty theft or fraud? The Ministry using Dementors for law enforcement would morally justify rebellion against it in my view, not only are they slavers they're also torturers on a scale that would make many dictatorships blush.
It's obvious that the Ministry a wicked institution, but it's also an incompetent one since the Dementors aren't even really loyal to them; they jump ship to the Death Eaters as soon as they get the chance to.