It is just an interview for the documentary, pre Berg's capture. It probably shows pro Iraq policy views, hence it was not used. Moore is not blackmailing the Berg family. They are communists and they and Moore figure the father can make a "family request" that the interview never be shown. But it is "criminal" that wew ill not get to see murdered Nick Berg in his own words. If the father agrees with such an approach, he is as shameless as we already knew him to be.
I still don't buy the coincidence that a traiter like Michael Moore who has publicly cheered on the terrorists, and hangs out with extremists like José Bouvé who did prison time in France for bombing McDonalds, just happened to meet up with ( by chance of course) some guy who would later be publicly executed by the head honcho in Iraq.