Your employer cannot revoke your workers' compensation. It would be stupid to attempt to get in the middle of this process because it could cost itself much much more in the form of discrimination lawsuits by you. You need to simply reiterate and remind that you are not cleared for DOT driving, showing the doctor's note to the employer while you explain and get yourself a lawyer to possibly sue for harassment and discrimination. Talking to an attorney is not going to cause any harm. You need to be armed with the right information before you decide your employer or staff has or have gone too far.