Welfare dependency and excessive use of the drug alcohol are linked, but we rightly don't see that as sufficient justification to ban alcohol. And substance bans have costs of their own: both the direct cost of enforcement, and the giving of a monopoly in the market for that substance to violent criminals, with all the ills that follow.
I'm just saying that I, who leans a bit libertarian, am coming peeved at my fellow libertarians who make out legalizing pot to be more of a freedom issue than ditching the welfare state (what used to be one of our main goals).
IMHO getting rid of the welfare state is critical to truly legalizing drugs or anything else.