According to the Moscow Post, John McCain spent most of his years of captivity in Voronezh, USSR.
While the circumstances of the release of this information are suspect, this information does go a long way towards a reasonable explanation for McCain's behavior towards Viet Nam POW/MIA families. These families had reasonable and compelling information indicating that a large number of MIA's continued to survive in Viet Nam long after the cessation of hostilities between the two countries.
Widely known sources reported that McCain yelled and demonstrated obvious contempt towards the members of POW/MIA families while he sat on various committees related to the POW/MIA issue.
If the Moscow Times report is true, it is clear that McCain had, and continues to have, a vital interest in the non-disclosure of all the facts surrounding the Viet Nam POW/MIA issue.
"Jack Mouse," "Johnny Wetstart," or "Insane McCain" -- there's alot one can find out about a person from their nicknames.