Perhaps, first, one should become aware of the legitimate roots of law and policy, and refrain from spouting irresponsible drivel such as, "The law making marijuana illegal was made back in the days were racism was accepted. Now we are in our politically correct nation, why do we still have our racist laws?."
Laws against the sale and use of marijuana are not racially motivated; but rather, are founded upon the belief that marijuana is an addictive drug, and that its use is a stepping-stone to the use of more harmful drugs.
These premises may be accurate, or they may be utter bunk; but if you begin your discussion of a policy (because laws are intended to implement policy), you should at least make sure that the policy actually exists, and forms the underpinning for the laws you want changed.
If you choose to attack a law, you should both attack the policy that you claim is flawed, citing persuasive reasons why it is flawed, and (perhaps most importantly) citing a more compelling and appealing policy approach, one which will achieve your intended purpose. If you (and all those who are of a like mind) succeed, then you will have convinced enough of hte electorate (and their elected representatives) of a compelling need, and the change will occur.
Or, you can simply call laws "retarded," and see what reaction you get from the various legislative and deliberative bodies which, by the collective and presumably honorably-intentioned acts of their members, past and present, implemente dthe very laws you seek to change.
When's the last time you changed your position on something you did because someone called your actions, "retarded"?
...three miles from BRONS, clear for the ILS one five approach...