here is an excerpt of an article about how PBS refuses to run certain left-wing documentaries:
snip
In 1997, PBS was scheduled to air "Out at Work," an award-winning documentary about three lesbian and gay workers' struggles for justice and dignity in the workplace. PBS suddenly cancelled, claiming it discovered that 23 percent of the film's modest $65,000 budget came from such "problematical" sources as a lesbian action foundation and some labor unions. One of the film's directors, Kelly Anderson, said: "None of the funders in question gave more than $5,000 to the project, and most gave $1,000 or less."
PBS official Sandy Heberer insisted: "PBS guidelines prohibit funding that might lead to an assumption that individual underwriters might have exercised editorial control over program content even if, as is clear in this case, those underwriters did not."
Journalist James Ledbetter asked PBS official Barry Chase if this decision meant that a labor union could never fund any program on public television that had to do with issues of the workplace. Chase replied: "Yes, that's exactly what I'm saying." However, corporations have been allowed to sponsor programs that featured their products. Financial institutions sponsor business news; in fact, "Wall Street Week" host Louis Rukeyser even has interviewed analysts touting certain companies with which they had an undisclosed financial relationship.
In 1994, PBS refused to air "Defending Our Lives," winner of the Academy Award for "Best Documentary Short." The film critically examines the problem of battered women. PBS turned it down on the grounds that one of the producers was a member of a nine-member prison support group concerned with the issue. The producers said the woman neither funded, profited from nor controlled the film, but PBS said the "perception" that shows are being "created to advance the aims of
group" is "as important as the fact."
In contrast, earlier this year former CBS and ABC news correspondent Jerry Landay revealed that three conservative foundations -- Bradley, Olin and Scaife -- subsidized at least 17 single programs or series on PBS from 1992 through 2000. All the programs served as "a platform for the views" of the foundations' grantees and their organizations. These included a program on "scientific creationism," another that blamed lack of self-reliance for problems in the ghetto, an attack on "political correctness" based on alleged "reenactments," a three-part series on the "gender wars," dominated by anti-feminist voices and a debate on "school choice" with 38 of 42 guests supporting public funding of private schools. Not only did these shows air, but there was no public acknowledgement of PBS violation of the "perception" guideline.
more: http://www.tompaine.com/feature2.cfm/ID/4631emphasis in bold is mine, not in original
my comment: there is a lot more where this came from. and since Bushco took over, it's gotten even worse. PBS is not left wing-- they are a mainstream, corporate centrist group that throws out a liberal bone every now and then.