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.

Are you ok with ciggarete smoke then if you are ok with marijuana smoke?

babies -> needed for civilization to continue

weed -> possibly negative effect on civilization ( https://pmc.ncbi.nlm.nih.gov/articles/PMC2424288/) , certainly not a requirement.