My understanding is that presentation did not include references to the McCanns. Those clips were inserted at a later date, presumably by one of the conspiracy theorists. As Arthritic Toe points out, it's easy to take selective clips to support your argument.
I don't think anyone would disagree that there was negligence on their part but, playing devil's advocate and assuming they didn't kill their daughter, what are they other than victims? As for Sarah Payne, that is different in that her parents know for sure that she is dead as her body was...
There may well be a differentiating factor due to perceived class. Compare the Mcanns with the Shannon Matthews saga. Who's to say there might not have been a fund set up and a large amount collected had it not be found the latter was a complete scam.