Does Dickens think that all criminals are bad? How do you know?

No Dickens actually has a soft spot for criminals. Things are not black and white in Dickens's world. Bad and good are not decisive terms to one's personality. Crooks often have kinder hearts and a more truthful view of life than so-called "gentlemen". Magwitch, although he had done some bad things, turns out to be one of the more sympathetic characters in the story.