What's fascinating to me is how an individual's own personal bias affects how they interpret any given source. CNN isn't extreme by any stretch of the imagination, though some people probably feel that way. This is consistent with the notion that as partisanship increases, many people will view information that contradicts their own opinion or perception of reality as false, or an attack, instead of a different point of view. It's harder to have a discussion about anything when people are spring loaded to assume the other side is arguing in bad faith. This mindset also makes it easier for people to believe increasingly outlandish things they might hear about the other side.
What is interesting on the chart is the relative mass of the partisan right cluster. That general space has seen a lot of growth over the past 20 years. With FNC and CNN being most people's staple media diet, I would opine that the daylight between FNC and Infowars is less than that between CNN and Jacobin or Daily Kos. This is also reflected in the chart. Vast swaths of our population - the electorate - are functionally illiterate on how their government functions, which makes them easy prey for politicians and con men that make impossible promises or invent insane conspiracy theories about their opponents. I don't know how we teach our society to be better consumers of information, but I feel like we're going to continue down this road until we address that.