This group is an offshoot of the loose confederation of a family members of Viet-era MIAs and those who expolit them. They believe that Vietnam held American POWs past the war's end in 1973, and continues to hold them, and that McCain has been part of a government cover-up.

I give them no credibility, and its doubtful that they will get any traction with the media, who know these people and generally dismiss their claims.

If you want to know more, go here. It's part of a website that debunks the mythology surrounding Vietnam MIAs. The guy who runs it, Col. Joe Schlatter, is no McCain fan but hates liars and con artists. Here's what he says about Hopper:

Earl Hopper, Colonel, US Army Reserve (retired)

+Hopper claims to be a "retired Army intelligence officer."  Horseshit.  Hopper once served as the Intelligence and Security officer for an Army post where his main job was maintaining the library of classified documents.
 
+Hopper is not smart enough to pour piss out of a boot with the instructions printed on the sole.

+Hopper has made a career out of spreading lies about the loss of his son, Earl Hopper, Jr., when his F-4 was shot down over North Vietnam.