You're not the only one wondering that...we're all waiting in the wings with McCain's own statment about how POWs were taunted with the things people like Kerry were saying.
As a former POW, McCain is a moral free agent. If he chooses to embrace Kerry despite the egregious harm Kerry loosed on him as a POW, that's his choice.
However, McCain has no right to demand that other POWs join with him in embracing Kerry. He has no right to condemn other POWs for honestly and even emotionally calling Kerry to task, especially in view of the fact that Kerry has made his Vietnam experiences the focal point of his campaign.