In the 2008 Emma Loach film Madeleine's parents mention the letters they get - the insults and the threats. They'll have received such letters no doubt every day after returning to the UK, from nutters nothing whatsover to do with online groups - everyone with a high profile does unfortunately.
You should tell the whole story TT. The infrequent activities of online groups is probably just a fraction of what they have had to deal with from genuinely disturbed attention seekers, and most of it is nothing at all to do with any of us.
Indeed
Kate mentions in her book that over the last four years they have been contacted by several people, who Kate presumes to be suffering from conditions such as schizophrenia and manic-depression. She says that some of them seem to have become 'fixated' on Madeleine and her plight
Some of them are very persistent, tracking the McCanns down again and again, weilding their piles of papers full of totally illogical 'fact' figures and symbols. Kate says it was draining and at times a little scary
So, it seems, the McCanns have been harassed by 'supporters' too, who have become obsessed with the case