2) If you haven't noticed there's sort of a huge movement to decriminalize it over the past decade.
3) Entire states have legalized it.
4) Meth, Heroin, Crack, Cocaine, Alcohol, Cigarettes; there's way worse substances out there.
5) Get the fk over it.
*Bonus round*: The only reason it's illegal in the first place is so that oil tycoons and other captains of industry could guarantee a monopoly in the sale of their respective resources at the turn of the 20th century.