What lie by Cronkite are you referring to?
During or shortly after the 1968 Tet offensive, on the air he stated as a fact that the war in Vietnam was lost despite the fact that the VietCong were decimated (in the literal sense) and North Vietnamese were seriously thinking of suing for peace until lies like his and the anti-war movement gave them hope. This was just his most blatent lie.
Overall media bias was as bad then as now. A guy in my hootch received a clipping from his mother describing how our base was nearly over-run an we suffered losses. The night in question there was one rocket that landed near the end of the runway causing no damage.
http://dianawest.net/Home/tabid/36/EntryId/965/-Cronkites-Offensive-History.aspx
http://www.wsj.com/articles/SB120226056767646059
Do a google search, you will find more.