Because old habits are hard to shake. You see, in the pre-Internet days, CNN and the rest of the lamestream press could lie and get away with it most of the time. But with the Internet they are finding that the spotlight of truth exposes their lies for all to see.
Good question. Ends justify the means ideology? The Democrat Party being infested with supporters of Stalin but Truman and FDR denying it to save the party? The media never calling liberals on their lies?
Probably goes back further but the Democrat platform of 1932 is an eye-opener. Once FDR got power, he did exactly the opposite of what the party claimed it would do before the election. That worked so well, Democrats held a two to one voter registration advantage over Republicans for decades and held the House for 58 of the next 62 years.