CBI Ron IS Michael Kirkland - just with a beard and a little extra weight.  He has been quietly manipulating PJ from the sidelines this whole time.  He IS Red John.

Gale Bertram simply would not have the time or the privacy, as head of an agency such as this, to have the geographical range to do all the things that Red John has done.

Reede Smith is not bright enough.  Besides, he hired on with the FBI too late - their background check would have caught SOMETHING suspicious.

Bret Stiles actually DID become friends with PJ after they shook hands, so Lorelie's statement would make no sense if it were Bret Stiles.

Sherriff Tom McAllister has the same issues that Gale Bertram would - not enough time, privacy, and geographic range as the sherriff of an entire country to do all that Red John has done.

Ray Haffner isn't smart enough and doesn't have the personal charisma necessary to get ANYONE to do something he wanted them to do.

Bob Kirkland is dead.

Brett Partridge is dead.

As we have all seen throughout this series, Red John moves his pieces around the chessboard from the sidelines, rarely, if ever, actually getting his own hands dirty with something as menial as actually covering up his identity.  This is his way of living the life so desired by someone relegated to performing menial tasks on a day to day basis.  This is the essence of what drives Red John - and THAT is CBI Ron personified.