Tell that to the people serving obscenely lengthy prison terms for possession of small amounts of pot.
I think you are making that up.
I think that VERY FEW people are in prison serving hard time for a "small amount of pot".
I think that most of the people doing hard time were either;
a) Selling drugs
b) Transporting drugs for sale
c) Carrying large amounts of drug money & guns
d) Violated prior parole conditions