Just because something is bad for you doesn't mean we need to criminalize it. Ex. Eating unhealthy foods, not exercising, watching too much tv, playing too many video games, being a democrat are all unhealthy for you, doesn't mean we should criminalize them.
I do not think drugs are great, I just do not see the point in locking people up for hurting them selves, all the while spending 50 billion a year to not curb drug use or drug traffic one iota.
And just for the record, marijuana is far safer than alcohol. Legalize marijuana and half the cost of the drug war disappears overnight.