A platform is content neutral, like the phone company, and does not interfere in any way with the content of what gets said on their networks (wiretapping in criminal cases is different). A publisher makes editorial choices and takes responsibility for the consequences of that content. It used to be a pretty clear distinction until online conversation networks came along.
In the early days, those of us who managed those online conversation networks, including big companies like America Online, argued that we shouldn’t be held liable for everything that the users say to each other, because for one thing, we would have to pre-approve everything that got posted, which most users would find intolerable. Or we would have to actively censor whatever we found objectionable. So for the most part people said whatever they wanted and dealt with the liability or libel issues themselves. In 1996 in the USA, Congress passed the Communications Decency Act that did a number of things, mainly related to obscenity and minors, but included section 230 which make online services immune from liability for the content posted on those companies’ sites. In 1997 the Supreme Court struck down most of the CDA, but kept Section 230. This was all before social media as we know it was even dreamed up.
So into this legal framework came social media operations that gained audience far beyond anything any other online service had ever seen or even likely dreamed of. And with the advent of the Facebook ‘news feed’ began the process we find ourselves in today where the companies actively manipulate what we see on our screens to maximize our desire to stay on the site, or return to it often, and to feed us a lot of what we want to see and hear so we might buy the things the advertisers show to us. Whether they intended it or not, this actively contributes to a more polarized society according to numerous studies and essays.
And now, Facebook has banned extremist individuals outright.
So are they a platform or a publisher? They say they are a platform when they want that shielding from the law and they admit to being a publisher when they want to get rid of what they consider to be hate speech or people who espouse violence.
But when the New Zealand mass shooter spread that video all around Facebook, Facebook used the shield of a platform to avoid liability for spreading it, but then they wanted to be a publisher when they banned it. And let us remember that while that video was viewed on their platform millions of times, they made money off the ads that ran along with it.