It's illegal. I'm against unlawful things.
Hmm, it seems that you are deviating quite along way from your original standpoint, but that's ok.
Why are you against unlawful things? I understand that you
yourself might not want to smoke weed, for fear of getting into trouble, but why do you care about others smoking it? What about people smoking it in places where it's legal, what's wrong with that?
If you in fact have nothing against weed itself, but only the fact that it's illegal, then perhaps you should help the campaign for the legalisation of it? That way there would be alot less people committing crimes, which is the bit that you disagree with.