Your argument seems to be based around the fact that you couldn't handle it, started smoking too much and got messed up.
People drink themselves to death, most have a drink on a Friday nights with their mates. Should it be banned because some people can't handle alcohol?
I used to have the odd spliff when walking the dog around the park, or to relax at night, when I felt like it, and now... I still have the odd spliff when I walk the dog or to relax at night. I can take it, I can leave it.
I don't smoke ciggies, never have done, never will. I know which would cost more and be of a bigger danger to my health, a 20 a day Benson habbit, or the odd funny fag when I'm in the mood.
Disclaimer - I don't really smoke it of course, nor do anything illegal for that matter. I'm just making it up, not sure why... I think its the weed.