The original commenter was suggesting that incarceration for consuming cannabis is irrational, not that citizens shouldn't be responsible at some level for the collective good of their society.

Additionally, the implied causal chain you've laid out is fallacious. Ignoring the vagueness of what "troubled" means exactly here, if it is "troubled-ness" that makes someone prone to both crime and cannabis use, then clearly it is the troubled-ness, not the cannabis use, that causes the criminality. And if the goal is to reduce criminality, as is implied in your post, then whatever causes people to become troubled must be addressed—which, again, isn't cannabis, as it seems being troubled is a prerequisite to using it.

This is akin to the classic example of banning ice cream to reduce the murder rate. Ice cream sales and murder rates increase in a correlated manner—but only because both increase in the summer.

Also, as a final point, the fact that drugs like cannabis are criminalized turns any connection between cannabis and crime into a self-fulfilling prophecy. The real societal cost to the criminalization of cannabis comes via the violence and destruction associated with any criminal marketplace. The last time we saw massive organized violence between criminal organizations over alcohol, for instance, was the last time it was criminalized—i.e. during prohibition.

But yeah, something something libertarians something something cultural decay.