Mandatory minimum sentences are a waste of time and money and have not been proven to be a deterrent at all. Also, on a moral and ethical level, there's something incredibly unbalanced about giving a low level drug offender a longer sentence than someone convicted of a sexual assault or equally violent crime (hi Brock Turner! 👋). A great book to read on this issue and criminal justice as a whole is The New Jim Crow: Mass Incarceration in the Age of Colorblindness, by Michelle Alexander. The truth about the "war on drugs" is pretty damning once you start looking into it.