Outsider77, sometimes we just have to face the reality  that emotions too often overpower facts and common sense. (See above letter, for example)
I think you'll agree that employers have every right to know if you are impaired at work for Any reason--  alcohol, pot, opioids, meth, lack of sleep, emotional crisis, hangover, whatever....
But they have No right  to test  workers for past  activities which do not effect them when on the job.
It's common sense and fairness, and someday Outsider they will drop their taboos and create, legalize, and utilize a procedure which actually does test for impairment. It could save a lot of lives and freedoms too.