It's simpler to explain in economic terms. You get what you incentivize. The google-dominated internet incentivizes page views for money. People are going to post what makes people click - shock, hate, gossip. Posting feel-good me-too stuff does not bring views. So you end up with an internet looking like this. Does it matter? I m not sure, the yellow press was always there and we did not end up with a new hitler every 4 years. Does google matter that much to democracy? I'm not sure its propaganda can be that effective. I think the best kind of propaganda is economy: give people the economic rewards they asked for, and they 'll quit being racist.