I am putting this here so I can find it later (and not have to write it from scratch every time).
Moral argument: NO ONE should have their privacy invaded to earn an honest living, much less to receive assistance when they are struggling. The only time it’s even remotely defensible is when someone is operating heavy machinery or otherwise directly responsible for the safety of others, and at those times the test should be for the person’s ability to operate that machinery — and that should include the effects of ALL drugs and illnesses which impair motor function. Until that happens, “drug testing” is no more than an excuse to exert power over others just for the sake of doing it.
Practical argument: Several states have enacted laws requiring drug testing of those receiving public assistance. In those states, the evidence is overwhelming: more money is spent on drug testing than is saved by withholding support from people who test positive for the substances being tested. The only purpose for drug testing recipients of public assistance is to pay extra in order to treat them like shit.
Pragmatic argument: The surpassing historical ignorance of those who would deprive the poor of food never ceases to amaze me. Even if there were no other arguments for keeping the poorest among us fed — if chubby bourgeoisie like me were all heartless, rapacious narcissists — the simple fact is that when the poor are kept hungry, we chubby bourgeoisie tend to find our heads in baskets. I like my head where it is, thank you very much.