Drug-screening, can I be told I can come back to work after I go to Urgent Care for testing?

I woke up late for work and text my boss, like I've done in the past, I said I'd be there as soon as possible (implying 10-15 minutes). I received a response that the owner (a seniel, 83-year-old man, who, to my knowledge, has no power over scheduling) said to take the day off. So I called my work to talk with the manager and figure out what the reason was for this and why all of a sudden he has authority over who does or does not work there. When I asked her these questions she immediately got defensive and yelled into the phone that I was a drug addict and that I needed to get help and get myself cleaned up. Shouting at me that she does not have time for my S***, and that if I wanted to come back to work I needed to go to ReadyMedic (an urgent care facility in Louisiana) to be drug tested. I'm not sure if the owners daughter, the legal and authorized licensee of the business knows of any of this matter. The manager implies to me that I am suspended or being released of my duties based on personal suspicions of my use of some illicit or illegal drugs. The fact stands that I have not received any verbal warning or written documentation of the accusation of drug use on- or off-site of the business during my employment history with them. Is this defamation, discrimination, or retailiation towards myself or my character? Is this type of conduct legal for an employer to do to employee? Who can help me with this issue I am having? And what legal rights, if any, do I have before risking my position in the future with the business?