Saying that scale is irrelevant makes me think you are intentionally obtuse about this. FB picks which newspaper's article to show you just like newspapers choose which journalist's article to show you. And just like newspapers give a tremendous amount of power to one individual (the journalist) compared to another (you), FB can do the same for individual articles and outlets. Except FB has the kind of reach no newspaper ever had or will. They give a podium for others to climb on, they decide who gets the front seats, and they monetize it.

For all intents and purposes they should be responsible for everything that happens on the platform regardless of where the content was picked up from. They should have a responsibility but this comes in conflict with their goal to to drive engagement and profits.

Their algorithm curates what people see, shows specific links, and influences opinions. And when you can influence opinions on such a large scale and monetize it we have a conflict of interest and even a weapon. FB and others have proven this in the past. Why do you think the media is regulated so tightly around election time? FB can take even a blog post and push it so aggressively right before elections that they manage to sway opinions but still claim they were just a platform.

The counter-argument is that it's easier than ever for an individual to find critical analyses of that information. If you were suspect of the information on TV in 1983 there was no one to tell you any different, unless you put effort into finding it.

Let's put it in terms other than politics...

In the early 1980s a full third of all households in the US watched the TV show "Dallas" every weekend. Was "Dallas" the greatest performance ever made or just the best option out of 3 choices?