"laywer - smawyer".....I'm just a poor junk dealer in Texas, however I believe you are both intelligent and have valid points. In actuality, both do have merit, and can be followed.
The "whammy" here is of course the ray. Since it is impossible for us to know that MI has definitively infected the ray (hold on a bit Stuart:rollface

, rays, sharks, eels, etc. may harbor ich, or may not harbor ich, I know of cases where the option given by syrinx was heeded with an eel. The fish were removed and treated with chelated copper in a QT, while the eel was left in the DT for 10 weeks. The fish were returned ich free, and were not re-infected. For some reason MI does not have the same affinity towards these species as most bony fish.
Since the OP is a good ol' boy from Texas, I will chime in again.
1. Do as syrinx has suggested, although Stuart may be right
2. Remove all (including the ray) and treat with a quinine bassed drug
3. Do not remove any fish, and maintain excellent water quality, and feed very highly nutritious foods.
4. Do NOT treat the ray with copper based drugs
In your situation, I personally would opt for #2, with #3 being my second choice. One thing the OP has not indicated is how bad the outbreak is.
I do agree with points from both syrinx, and Stuart. I also believe that sometimes approaches offered somtimes seem to derail from what the OP was originally asking.
SV