But in this case I have fallen victim to an Internet prank. Johnson’s response to my joining this group was so swift that I suspect that the group itself, and its invitation that I join it, was a hoax and a setup

Robert, the very fact that you even consider the possibility that Charles set up a fake FaceBook page and invited you to join it in order to (further) discredit you, which is what you’re clearly implying, speaks volumes about your fragility of mind. Get a grip, man.