1. People who use illegal substances, even habitually, are not necessarily on a downward spiral of destruction.
Are you now going to argue that addiction is a good thing?
Sure there are exceptions to every rule, but come on, you cant sell black tar heroin as just an occasional fun thing to do when you're bored (for example).
Habitual marijuana use, specifically, is something I've seen as something that doesn't fit with that model.
Purely anecdotal. The DSM V still lists Marijuana addiction as a diagnosable issue.
Nor is marijuana the only drug tested for or used.
Certainly there are some people who would use all available resources to get another fix, but definitely not all. Your premise appears to me to be false.
Not in the least. Even non-addictive illegal drug use isn't something these people should be spending taxpayer dollars on. That is not what the aid is for.
2. There are means to help ensure accountability of the money being used without resorting to drug testing. Better tracking of how one spends government assistance, for instance.
There already exists a significant black market for food stamps themselves where people sell entire books of food stamps for illicit substances. Anything you suggest along these lines is going to be exponentially more invasive than a simple drug test done to enter the program.
3. I don't see how denying aid is going to help in most of these situations when the support system to help them overcome their problems is spotty and shoddy.
It's going to make people choose from being responsible and getting their lives on track as opposed to continue leeching off the public in irresponsible ways.
I don't mind giving aid to someone deserving of it; but I don't want to pay for someone's drug habit be it addictive or not. The least we can get as taxpayers is reciprocal behavior from those asking for aid to not spend that aid on drugs. It's a win/win scenario either way.
Any evidence of drug use found in such an administrative search should not be used for prosecution purposes if the 4th has any meaning.
I agree and I've already said there wouldn't/shouldn't be any prosecution or charges preferred based upon such a positive drug test. Thanks for confirming what I already pointed out.
And fwiw, the military had a similar policy on this called 'limited use' for people who came forward and asked for help with their addiction. They would still probably be discharged but would get drug addiction treatment and an honorable discharge on the way out. At the very least they would avoid punitive military justice action.
Some people are really bitter about welfare. Disproportionately.
A very bad mischaracterization. Some people are more than willing to give, they just want to see what they give used in the manner which it was intended.
Nothing wrong with that at all and its hardly disproportionate.
Not to mention irrationally.
Who's been irrational?

I'll just chalk this up to you being unable to address the point, and you'd rather just label those that don't see things your way.