... If TPTB are outright banning Most Haunted fanfic, then they are creating a situation where it is simply going underground; it's not going away, merely, it is being circulated by those "in the know" as it were. As this type of circulation is unseen by any moderators, it is unregulated, i.e. anyone can upload just about anything they like. Some stories will be extreme, some will be violent and possibly some will be pornographic in nature, but the vast majority of authors just want to upload their interpretations of the series for other fans to enjoy. TPTB don't have to read it if they don't want to, but for fans it is a way of connecting with eachother and sharing their thoughts. The majority of fans do not mean to cause any offence to anybody who is, or who has ever been, in the team.
If there were a centre for the fans to upload their stories, they could share their ideas and thoughts in a moderated way, anything from humorous stories of friendship, to carefully constructed love stories, all laden with creative merit.
And, besides, is there any real difference between Real-Person Fanfiction and Historical Fiction or Political Satire? The people about whom the stories are written today will become the historical figures of tomorrow.
This is my case, that is my evidence, and your opinions are yours to make, but I can only see positives in giving the fans a creative outlet.