Probably the reality is that the internet is filled with propaganda. Every site. Every forum. Even HN is filled with anti-(put pretty much anything here) propaganda.
Try to ignore the noise and tune in more of the signal. That's about all you can do really.
I'm not sure banning websites will do much for you, as you two are rightfully pointing out. You ban a website in Brazil? Well, OK. You get to broadcast most of the propaganda in Brazil, but the rest of the world keeps getting the anti-Brazil propaganda. You ban a website in China? Well, OK. You get to broadcast most of the propaganda in China, but the rest of the world keeps getting plenty of anti-Chinese propaganda. You ban a website in the US? Same thing. You get to broadcast most of the propaganda in the US, but the rest of the world keeps getting plenty of anti-US propaganda.
So we need a mechanism to decide if a specific type of propaganda is acceptable or not. And, if governments get involved, typically they will start restricting propaganda that is truthful but threatening to their chances of holding power (ie, people pointing out the flawed nature of the powers that be). It is better force people to fight propaganda with counter-propaganda and let individuals make their own mistakes.
The problem is information flow. Propaganda vs propaganda, nowadays, is in-group information and desires fighting against other in-group information and desires.
The lack and importance of truth, facts, the bread and butter of journalists, investigators and scientist, gets out of focus because of governments and other actors blocking access to data, events, locations, partially because often enough, people asking for access tamper with the evidence or start to run all kinds of narratives that would impede an investigation and results that could be 'useful'. There is, of course, much more to all that.