This just isn't true. More biased than Bill Moyers' stuff, or Michael Moore's?
Some of the Frontline programs in the last several years have been damn good. (They don't have a fixed staff of primary producers and journalists, so the shows vary quite a bit.) "The War Behind Closed Doors," last season, was a very fair account of the rise of the "neocons" and the doctrine of preemption. A few years back they ripped Clinton mercilessly (and justifiably) over Rwanda. Last season there was a glowing and haunting portrait -- "The Man Who Knew" -- of 911 hero John O'Neill, the FBI bin Laden expert who left the agency after it repeatedly undermined his efforts to identify and expose our enemies, and went on to become head of security at the WTC. One of the CIA's finest field agents, Bob Baer, was also profiled as part of program called (IIRC) "Tehran and Terror". Previously they have done multiple documentaries highlighting Saddam's brutality and beligerance. "Battle for the Holy Land," which profiled both an IDF unit and a Hamas cell during the current "intifada", was very fair to the Israelis. It described very clearly the rationale and criteria behind "targeted killings," and portrayed the dedication and professionalism of the Israeli army.
Even in the current show, with the producer and interviewer Smith obviously biased (he frequently argued with his subjects in the irritating and mewling way that libs have) there was still significant airtime given to truth tellers like Kanan Makiya and Richard Perle.
I've found that Frontline is nearly always worth tuning in. Yes, they still do shows that are intolerably biased, but then that's evident quickly and you can always change the channel. But by writing the show off you've missed some really good stuff.