I think Trump was just being Trump and trying to be funny and inserted foot in mouth without thinking about what he was saying. He just happened to say something that was sacrilege to vets who were POWs and was a little disrespectful in that regard. I also think Trump was also making the point that McCain has used his being a POW status as a “marketing tool” to keep himself in office. The main reason you keep hearing it over and over agin in the MSM is because the left want to use this to steal his thunder and remove him as a threat. Having said that I won’t vote for Trump. My ote goes to Cruz.
You put your finger on it. Trumps's remark (I like those that weren't captured) was flippant and no more than half serious and parallels a Chris Rock routine which wasn't funny either. None on the "analysts" I've heard/read/seen (except you)have made that point.