A lot of people like to drink alcohol
A certain percentage of them become alcoholics who drink while driving and cause accidents and death
Now I'll rephrase your conclusion slightly to see if your 'logic' holds up:
"The behavior of drunk drivers is not relevant to the question of whether or not there should be restrictions on the sale and use of alcohol."
It doesn't.
Patently false. Don't fight logic. A=A.
But so you don't misunderstand my position, I am not against restrictions on the production or dissemination of porn. I just don't believe that the "serial killers" argument is either correct or helpful to the debate.