Talk about insulting, I was recently asked by a young 1stLt if I went to medical school. And it wasn't mean't to be an insult, like I did something stupid and he asked if I actually went through medical school, it's just that (at least on the green side) a lot of folks think we're not real doctors. Like we went to an MOS school or something. Granted they do see their fair share of IDCs, and they call corpsmen "doc," but still.
Medicine is awash with people wearing white coats. NPs, PAs, pharmacists, CRNAs, nutritionists, respiratory therapists, food service specialists, and people who think the thermostat is set too low.
When I got credentialed at the VA a while back, I had to get an entrance physical done. The NP who did it introduced herself as "doctor". There are too many people in healthcare pretending to be more than they are.
Too many administrators with ulterior motives for blurring those lines. Fabricating terms like "provider" to gradually make everyone interchangeable, to deceive patients into thinking that one "provider" is just as good as another, so the hospital has cover to spend less money to provide lower quality care.
As you point out, the Marines see a lot of Corpsmen, IDCs, and PAs, all of whom they call "doc" ... there's a lot of history, camaraderie, and shared suffering behind that, so it doesn't bother me. Of course, they called me a "Battalion Surgeon" back in my GMO days when I was a couple weeks out of a non-surgical internship.
It's probably a good thing that 1stLt cared enough to ask who was actually taking care of him. It's not a patient's fault the system has been carefully and consistently lying to him for so long. Don't be insulted by the fact that he's been fooled, be angry at the lazy credential-inflating pretender ****s who fooled him.