The principle I'm speaking of is judicial discretion. For a judge who hears the facts of the case, to impose a just and reasonable sentence, given the offender's personal circumstances, given the offence type and the circumstances of the offence...a minimum sentence removes that discretion. There are many cases in which it could result in unjust results should the minimum sentence be passed.
If there were a demonstrated link to show that mandatory minimum sentences deterred conduct, made us safer, perhaps my position would be different. There simply is not. If there were evidence that judges were getting it wrong, were imposing lenient sentences and there needed to be more denunciation, perhaps my position would be different. Unfortunately, the evidence isn't there to bridge the gap between the purpose of the legislation and the way the legislation tries to implement that goal.