This theory has 2 questions for you.
Question 1 to those who think Kirkland also hunts Red John:
There is a missing piece in the theory that Kirkland is also hunting RJ.
If Kirkland is hunting RJ as well, and talked to Lennon to know whether his cover was blown or not, why would he keep everything from Patrick?
Who is a better friend than Patrick Jane to hunt Red John? He has a hell of experience, he is smart.
Kirkland didn't talk to Lennon at hospital about Red John at all. In this case, your theory assumes that Kirkland knows RJ already. Why else would he not ask who RJ is?
If he is after RJ and knows his identity, what is all these episodes about? Why doesnt Kirkland kill RJ already? Only explanation would be that you can hardly reach RJ, because he is imba protected like a president or something. This won't make sense for the series.
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Question 2
Where the hell is Bret Stiles? He is missing since the murders in barn were found out. Remember the episode. The sheriff or whatever finds the bodies in barn, and learning that those murders are associated with the activities of Visualize, Patrick and Lisbon? go to Visualize. But, Bret is not there and the guy says that "Bret Stiles told me to help you in the best way", before even case is explained.
So, Bret Stiles heard about the discoveries of bodies in barn. How?
He left the town avoid questioning. Why?
And of course, what is he doing all this time?
Bret Stiles is not around for a very important and specific reason. And I think it is the key to know more about Red John. Why Patrick quit chasing it, i have no idea. In fact, Patrick's actions never make sense, since he is supposed to be smart.