The danger of a mandatory minimum sentence is that it can act like an incentive, in that if a person is charged with an offence and is facing a mandatory minimum sentence if convicted and were to plead guilty to a lesser offence in order not to have to face that mandatory minimum sentence, it incentivizes the person to plead guilty to an offence even if they're not guilty of the offence. Even if the Crown can't prove the offence, they're incentivized to plead guilty just to avoid that mandatory minimum sentence.
Unfortunately, many of our accused who go through the criminal justice system don't always have the benefit of counsel and make these decisions with a cost-benefit analysis, and if they say, “Oh, if I just plead guilty to this, I don't have to go to jail for 12 months”, they may very well do that.