Yes, it is. Of course, there's a different irony in the fact that all mind-altering substance were legal in 1900 - all of them, including heroin - and 1900 was like, well, 1900.
Widespread welfare does introduce a different dynamic, but that's a dynamic all its own. The Controlled Substances Act has not prevented the welfare culture from getting out of hand. Nor would Prohibition have, come to think of it. It's cold comfort to know that you've been flash-mobbed by fifty clean and sober ferals.
The way I see it, there are two arguments that the drug prohibitionists rely upon with regards to the welfare culture:
The sad state of the welfare class is completely entangled with drug prohibition. While excusing none of the other causes — sloth, promiscuity, ignorance, illegitimacy, etc. — drug prohibition has made a bad thing much worse. The lure of drug dealing kills or imprisons an absurd portion of the young men of that class, and renders them ineligible for most employment when they get out of the game. Drug gangs are the main source of structural criminality and violence in their communities. Drug money deeply corrupts institutions that could be relied upon otherwise to stabilize or bring order.