edit: if you're going to down-vote something which is plainly constructive and well thought-out, you should try to articulate a response.

[1] propaganda, noun, derogatory: information, especially of a biased or misleading nature, used to promote or publicize a particular political cause or point of view.

His comment is claiming that fake political news should be distinguished from the fake tabloid style news (bigfoot sightings/alien abduction/etc. that we've become accustomed to in the grocery store checkout aisle). The former is propaganda, the latter is not.

This distinction is correct, in terms of everyday usage of the word.

Your claim that "everything is propaganda" is plainly false. An author having a political agenda is not sufficient to render an article propaganda. This would be similar to claiming that every article written by someone with sexual desire is "pornography." It's plainly ridiculous, unless you are operationally defining "pornography" to mean something other than it does in everyday written English.

Things that are propaganda:

1. fake news stories disseminated with the express intent of influencing elections, which are known to be false by the author of the article / editor of the publication / etc.

Things that are not propaganda:

1. stories about bat children in supermarket tabloids

2. your comments

Things that might be propaganda:

1. fake news stories about political figures that appear in tabloids that also produce bat-child news (the article is false, the article might publicize and promote a political cause, but it isn't clear that it is a tool deliberately crafted to do that). What would clearly be propaganda in this situation though, would be a liberal/conservative/etc. spin site republishing a fake tabloid news story about Clinton/Trump that they must in good faith know is false).

[1] https://en.oxforddictionaries.com/definition/propaganda

This is a fundamentally intellectually dishonest argument. There is a difference between making an argument with an agenda, even reporting news with an agenda, and propaganda. You can't just wash everything in shades of gray and shrug while saying "who knows what is truth? or what is false? oh well, guess we'll never know". Truth exists, and it is possible to determine what is true and what is not. Propaganda is passing off knowingly false reports in order to advance a political goal. It's a real thing, which is why there's a word that people created to describe it. Pretending that it's not propaganda has as much claim to legitimacy as any other news is not only wrong it's incredibly dangerous.

"The sky is blue."

That statement isn't untrue, it is objectively observation with one's eyes or using spectrometers in the case of an individual who is colorblind. It isn't binary, statements can be rated on a range of truthfulness from false propaganda to very objective...and, arguments that are isomorphisms of "all sides do it" are harmful because they essentially justify parties who benefit from such propaganda.