I wish Peter well with whatever this is that he is struggling with. And you are right this is recent. Even as quirky as his trip out west was it was an interesting read. But even when he was on track and staying in his own thread it didn't stop a few to go to the thread and toss in some pot shots, attempt to derail his thread, light a fire under him, I find that equally as unsettling. I shared a couple of conversations with him yesterday and can see he is struggling and I have empathy for that. I certainly wish him well and hope whatever he is going through he'll come to terms with soon. I hope for him to be well.
Actually, he first used the "I was only joking" response when called out about an "untruth" in a thread he started in 2003. The incidences only increase when he finds new, sympathetic people who allow him to post this "unsubstantiated" information. I won't call them lies, because I don't think he knows the difference. But, encouraging him only makes him think this is accepted behavior, and you enjoy his input, so he does it more - and the posts get more outrageous.
Again, some people should not be posting in discussion forums. Sympathy and empathy can only go so far - we can't give him whatever it is he needs, and are not doing him any favors by tolerating his behavior. Remember the old saying "Sometimes it's cruel to be kind?"