The fact that most Muslims haven't gone on a murder spree, doesn't make up for the fact that the ones going on murder sprees are Muslims.
The fact that most queers haven't raped little boys does not make up for the fact that the ones raping little boys are queers.
The core of the problem is not what "Most" do, it's what a significant percentage of people who are given to those sicknesses do.
And the number of mass murderers nor serial killers is not a significant percentage of the millions of American pot users.