Please don't change; we're not through here
What is real?
The higher credentialed medic determined that his patient was a BLS call, felt no need to intervene, he did NOT apply the O2 himself
He handed the care of the patient off to the OP.
It's the OP's patient now!
POLITICS, Part I:
He asks OP to put the pt. on O2. I forget, did he say how many LPM?
By now, OP should know if applying the O2 will harm the patient.
If no harm, apply the O2.
If "potential" for harm but no imminent danger to patient
Apply the O2.
Why? Because if OP moves fast enough that patient will be out of sight of the medic, in OP's ambulance and UNDER OP's CONTROL and legally, OP's responsibility.
END POLITICS Part I
Now go back and do a THOROUGH assessment.
If OP's conscience says give the Medic his due unless OP is sure he knows enough to countermand his decision, keep the O2 on while pt. gets assessed.
Adjust or remove O2 according to the current assessment.
Document.
HINT (You owe me ten bucks!): the status of patients often change in transport!
POLITICS Part II:
You'll notice no mention of even talking to the guy. Why? Because under those circumstances OP is not going to be able to educate him, and...
under those circumstances OP will soon be in charge. NOTHING ELSE MATTERS other than the welfare of the patient!
Moral of the story: Understand when you become in charge. If you can accelerate the process of you getting there, then do that. Once that happens, YOU can be the guy who says: "Just because*" and then let the guy downwind of you agonize over how to handle you!
Your friendly firetender
* While, of course, you back it up with your best clinical judgment.