Always thought that John's worry over Sherlock's name being smeared by the media in TRF was due to basic empathy, but just realized there's more to it-- He's seen it done before, with another good friend who was destroyed by the media, who became a complete recluse, whose only interaction with people now are getting death threats from them. He knows someone who has never recovered from being publicly torn to shreds the way like that, and doesn't want to see it happen again.