To the degree that your contention is true, we can call a prosecutor "bad" who turns B's into A's through careerism or other motivation to intransigence. That some prosecutors will seek to decide for themselves who is an A and who is a B is an occupational hazard for them, and politically I would call it a form of mental illness.
I recall reading a critique of the US prison system which said it has a tendency to turn B's into A's. I'm not sure how true this is, and I can't quite recall the exact mechanism which was outlined -- I think it was something along the lines of giving B's months or years of 24/7 exposure to an environment where being an A is common and socially acceptable.
