WRT #5 - what is wrong with experimentation and learning on one’s own instead of just believing what they are told?
Who is "one"?
To the decriminalizer's mind, "one" is a twentysomething college graduate with extensive life experience, a supportive family and ample amounts of demonstrated personal responsibility who decides to try a substance for his own amusement.
In the real world, "one" is a poorly-supervised twelve year old with no judgment, poor impulse control, acting under peer pressure with no guidance from wiser people who have his best interests at heart.
Who "one" is matters.