Rigsby is the killer, Red John, because he has the criminal father figure and always seems to be a little too gullible and overly amiable... all the time. tis not natural, methinks. He is Wayne Rigsby, not Clark Kent.
Additionally, when Van Pelt had the killer FBI dude for a boyfriend, Wayne told him that he ought not hurt Van Pelt and then made a determined threat to him saying, "You will have to deal with me!" 

Where is Rigsby when the coroner in season four is killed at the blind lady's house? However, Rigsby is around when Red John is online spying on CBI, but I think it was just one of Red Rigsby's minion.
One has to think that Patrick went to CBI for a reason after his family was killed. Director Bertrand was not there yet, nor many others. Patrick was trying to follow a lead that ended at the CBI, from which he has been flushing Rigsby out from the beginning.
Rigsby is just too clean cut Utah to be anything but cultish and psycho killeresque.
Cho? Get serious!