As a guy that falls somewhere on the spectrum between agnosticism and atheism—a “god of the gaps” guy, as a nod to your comment about the hazards of scientism—there’s one thing I know about Catholic priests in particular is that you folks are awfully well read. 

Anyway to respond to your question: I dunno really. In general I don’t think things should be illegal because some people misuse them. Not everyone will watch porn and become hopelessly addicted just like not everyone will buy guns and start murdering people. Let those people fail but also let there be strong safety nets to catch them and set them right… be they strong communities, institutions of faith, government programs, or whatever. 

Full discourse in case my bias is showing: I do enjoy me some occasional cannabis and pr0n