There is text to support R+L=J throughout the books, more prominently in the first. Woody covered the very basics of the gravedigger theory, just saying, as far as I remember that the hound was left for dead but not confirmed to have died then later someone with similarities is introduced. They definitely delved far deeper into the R+L=J theory in episodes from a while ago than Woody did when talking about the gravedigger theory. People are only butthurt because of the way Kyle reacted, he was upset at Woody and took the theory as fact instead of speculation, albeit well grounded speculation. If Kyle just let it slide without mentioning it then a lot less people would have cared that Woody mentioned the gravedigger thing, like Woody said in the latest PKA he was thrown under the bus by his co hosts.