1) Internet companies, specifically, and the internet in general have this anything-goes libertarian type attitude to their platforms and it's clearly caused tons of problems and going to cause tons more. How easy it is for children younger than 10 years old to stumble across hardcore, violent porn. How easy it is for anyone to say any genocidal, horrifically disturbing thing they want and have thousands of people reading it at the same time and connecting over their shared horribleness. These aren't good things. We had "Viewer Discretion is advised" and TV censorship for a reason. It was taboo to go out and shout racist nonsense at the top of your lungs for a reason. And the people who by and large run the Internet (Silicon Valley-ites) seemed to buy into the idea that restrictions are always bad and that freedoms are always good, in every scenario. That just isn't the case.
2) At the end of the day, propaganda works because people resonate with it. You can blame Facebook, blame the Internet, blame people's stupidity, blame the conservatives, whatever you want. But at the end of the day, people had more than their fair share of warning about what they would get, and still a ridiculous portion of the American population walked into a voting booth and picked a guy known to lie, cheat, and lie further his way into everything he's ever done. A man who has settled numerous lawsuits over racial discrimination, defrauding students, fraudulent advertising, etc. A man who didn't need to have his racist statements decoded because they were just openly and unabashedly xenophobic. A man who never held any kind of elected office in his life (not even 3rd grade class president). At the end of the day propaganda doesn't work if it's selling something people don't want. ISIS propaganda is slick and abuses social media but it's not exactly something Americans are yelling at their families over and breaking up long friendships because of. People want to kick out hard workers who will do the same job as them for less (even here in Hacker News we see the same kinds of comments from software engineers fearing the H1B visa-holders will drive their wages down). They want handouts and for their lives to be easy without having to put in extra work. They want whiteness to be the default in America forever. People will have to deal with this fact. And no amount of analysis or correction in Silicon Valley will change that.