If hard drugs have a lessened stigma and are more readily available, more people are going to use.
This is actually demonstrably false. Look at the statistics in Portugal since they decriminalized.
Full legalization would be a little different, sure, but I strongly doubt you’d see an increase in hard drug use with that either.
For this increased negative possibility, the benefit is what? Greater freedom for people to mess their lives up as drug addicts?
Oh, let’s see…fewer people incarcerated for nonviolent offenses, less money being poured into a losing “war on drugs,” fewer deaths from gangs and organized crime since any black market in drugs post-legalization would be massively less profitable than it currently is under criminalization…just to name three things.