Weed is not addictive. I'll grant most of your other points about it being difficult to think for some people like me and you. However I have known and know many who are as productive, if not more, because of or despite their substance of choice.

For me, I really don't give a damn what kinds of drugs people take beyond heroin, crack, meth, and others that have a clear history of detrimental effects on the individual. As long as you are rock solid and reliable, that's all that matters.