I'll listen to a medic if they give a good reason. Even if they're just covering all the bases, they should have a better reason than "just because."
I will listen to a medic because they are they are a higher license level. They do not need to give a good reason. For crying out loud, it is not like he was asking the basic to do something above their license level.
Maybe here on the internet world you can just challenge every little thing a medic tells you to do, but in my state and on my service if you have a higher license level you are in charge of the patient.
The medic was transferring care to the basic with the instructions to put the patient on o2... once in the rig if the basic wanted to discontinue o2 therapy after the assessment... then so be it. At that point it is their call... dont get so butt hurt just because someone told you to do something.
I have used the term "just because" with a smile and a wink in front of a patient before because sometimes it is more relaxing for the patient to think that the care and steps being taken are precautionary instead of giving specific clinical reasons.