Come on. There are plenty of counter examples Sam Johnson for one...
http://www.samjohnson.house.gov/
"Sam Johnson returned home to Texas after serving in the U.S. Air Force for 29-years as a highly decorated fighter pilot.He flew combat missions in both the Korean and Vietnam Wars and was a Prisoner of War in Hanoi for nearly seven years."
Yep. Good man. I guess he knew McCain in POW camp.
BTW, I haven't noticed much, if any support for McVain from any of the former POWs who were in the Hanoi Hilton with him. That, to me, says a lot about him.