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.