Apparently, I was mistaken, I guess he was in the Green Beret; but I refer to this post:
post #302, by sneakypete to Rodney King:
Rodney King: "I think I recall that you were once interested in whether or not this guy was actually a Green Beret."
sneakypete: "No, if I remember correctly, he checked out."
An admittedly cursory web search I did found no corroboration yea or nay from "official" sources I know that Maher was actually in SF. If the Green Berets are anything like the Navy Seals, there are plenty of "vigilantes" out there ready to pounce on anyone who claims to be a Seal when they're actually not. And none of these have come forward to deny that Maher was a Green Beret. So, until evidence is presented to refute it, I guess he was.