In case you missed it, "D.O.A.P." is the British film which uses a combination of documentary techniques and digital editing to create a fictional film about the assassination of President George W. Bush in 2007.
CNN turned down advertising spots because of the "extreme nature of the movie's subject matter."
NPR turned down underwriting because it wants to avoid notions of conflict of interest. The feeling is this film is likely to generate news and the network doesn't want to give the impression it is covering the film because of the sponsorship.
Given the timing, now less than two weeks before the mid-term election, the networks decision is not surprising.
However having seen a slew of fairly gruesome "Saw III" ads the last time I turned on the box, it's clear that "extreme nature" is in the eye of the beholder.