Because had we deleted all the posts that were worthy of deletion contained within it we would have lost half a thread, and what remained would have made no sense.
We would like to remind folks that Mumsnet's central philosophy is to make parents' lives easier. The McCanns are parents, they haven't been found guilty of anything and they have lost a child. By all means discuss the issues around this tragic case but please don't attack them personally here.
Thanks,
MNHQ