There is bias and there is ultra-bias (fake news). FOX News settled out of court admitting in their action they were complicit to fake news!
On the other hand, I agree that it seems that CNN slants its news in favor of the liberal POV. But then they are, for the most part, made up of journalists that have graduated from a Liberal Arts program (I know of no "conservative arts" programs). They are guilty of reporting the news in an historically approved fashion. If CNN's reporting tends to be liberal, there is great precedent for that.