I will never understand people who say things like this.
Because there are still murders, should we stop arresting murderers?
Because people still B&E, should we stop arresting burglars?
Because there are still assaults, should we stop arresting assaulters?
Because there is still child abuse, should we stop arresting abusers?
What in the world are you thinking?
There is a vast difference between the crimes you cite - where another person's rights are clearly violated - and drug crimes, where NO ones' rights are violated.
Think about it.
NOBODY ELSE benefits in any way.
I will never understand so called "conservatives" who claim to support freedom but allow and support government to interfere in our private lives by telling us what we can or can not put in our body.