Fred Kaplan thinks that the Clark McCain conflict is rooted in an old military rivalry:  "Clark was an Army infantry commander during the Vietnam War while McCain was a Navy aviator. As a rule, the grunts hated the flyboys." I do think that there's something else going on with some military types not really liking McCain. If he were a little less crude in advertizing his own military experience - some things really do speak for themselves - he might reduce some of the crankiness.