I do not know about the legal issue of this but I would also be roaring with anger and fighting it.
You made a good point that so many people who just want drugs, etc go to the ER and it makes the honest ones like ourselves end up being treated like the violators when we have to go to the ER. I agree with you.
I have no problem with any Dr. testing me...AS LONG AS I KNOW IN ADVANCE what they are doing and why. To hide it from you then charge you for it was wrong in my opinion.
Good luck fighting it, don't give up.