Is that, having been a POW, somehow enhances his ability to be Command-In-Chief (as Clark pointed out). The only thing his experiences can make him an expert on is POW treatment and torture. Unfortunately his stance on those issues have shown us just how much his experiences colours his judgements, namely, not at all.
As to "I was a POW" being a knee-jerk answer, consider if he becomes prez and bombs Iran. He'd probably use it as a justification for that as well. John McCains POW statements smells alot like Bush's "they are terrrrist. They hate our freedom"-spiel.