Propaganda = any mass communication intended to change political opinion.
The owners of the various cable networks have ideological goals, and they leverage their media ownership to achieve those goals. Editorial independence is extremely limited on cable news, and this control is actively used to shape the opinions of the audience. Therefore, propaganda networks.
People have this idea that propaganda is “fake news”. That’s not what it is; only the crudest of propaganda uses obvious falsehoods. Sophisticated propaganda relies upon selection and emphasis and tone. Partial truths, false balances, rhetorical sleight-of-hand.
And often not even that; you can also do propaganda just by telling plain, unvarnished truths that advance your cause. Propaganda is a tactic, not an ideology; it’s ethically neutral, and can be turned to good or evil. MLK’s “I have a dream” speech was propaganda.
The difference between CNN and North Korean state television isn’t that CNN is journalism and KCTV is propaganda. They’re both journalism, they’re both propaganda. The difference is that CNN is extremely sophisticated and subtle propaganda while the Korean stuff is extremely crude and obvious.
(the other difference is that KCTV serves the North Korean state while CNN serves its owners)
Everybody uses propaganda. If you think that one faction doesn’t, that just means that one faction is really good at it.