Some people say the same about the smell or noise of babies. It's not a very strong argument for getting ones way in controlling others.
babies -> needed for civilization to continue
weed -> possibly negative effect on civilization ( https://pmc.ncbi.nlm.nih.gov/articles/PMC2424288/) , certainly not a requirement.
Are you ok with ciggarete smoke then if you are ok with marijuana smoke?
If you truly think that "having babies" and "smoking weed" can be compared in any meaningful sense like this, I'm not sure what to tell you.