Many claim that McAllister is too old, but...

He is said to be 45 years old in his S01E02 appearance, which makes him approximately 50 years old now in 2013. The young Red John was at the Elliston Farm in 1988, which would make the Sheriff 25 years old at the time. Nick Nordella is playing a "young man" in episodes 7 & 8, which many think is the young Red John. Nordella is currently 25 years old....

I can see a scenario where Stiles shepherded a young McAllister to focus and rehab a troubled man. He ended up turning a dull knife into a scalpel. This is why he helps Patrick somewhat, he feels partly responsible for his family's murders.

Of course Stiles could be RJ himself. I've just enjoyed the whole storyline. My first choice was Bertram over the past years, but I'm gonna stick with the two best and most entertaining actors' characters:

Stiles and/or McAllister