Not that I like social media or tech companies (I detest them). But it's not a special case. Media companies, cable companies, newspapers, etc. They've all enjoyed the ability to manipulate and 'guide' what people see and what opinions they form, for a long time. It's nothing new.
Really, it's extremely new. The feedback loop for old media was very coarse. They knew how many newspapers they sold and had an idea of who the repeat customers were. Editorial could be said to be linked to bumps in opinion polls, but only very loosely. Nobody knew how or if anything worked. It was all theories and snake oil and "conventional wisdom". The old adage was that 50% of marketing was effective but nobody knew which 50%.
For old media to have the same qualities as new media, newspaper publishers would have to know in real time if you were a new or returning reader, how long you spent reading page 32, which article you talked about with your friends, who your friends were, what their and your demographic profile was and then be able to serve up customised content within an instant based on all of those factors. And then say that they aren't responsible for any of it because they're just a platform.
Really, the only thing that old and new media have in common is that they are broadcasting words and images to the general public. The comparison ends there.
Yeah, what's the worst that old media could do? Print uncritical, false claims about weapons of mass destruction in Iraq than lead to hundreds of thousands of deaths.
Being able to manipulate what 100s of millions or billions of people see every day on their screens is an unprecedented amount of power.
Democratic nations are not going to tolerate these companies much longer.