It's not a "marketplace of ideas", in practice it's a used car dealership. Just about anybody with the slightest bit of cleverness and free time can convince any trusting person of anything whatsoever, no matter how horrible, given enough exposure.

So the alternative is to create "oracles of truth" that cannot be questioned?

That's just the opposite idiotic extreme.

Who said that? The range of bullshit information you can find at a moment's whim remains extremely high, in fact higher than it ever has been in history.

That's a sign that the system is working as intended, providing publishing ability to millions that never had it before.

Any time that's not happening, you should be asking:

1) who's gatekeeping this forum? what are their motivations or objectives? to whom are they beholden?

2) who always gets access? who always does not?

3) what personal information or other information do they have to give in exchange for access? who's excluded as a result of these requirements?

4) how much access do they get? how many posts are they allowed to make? how much audience are they allowed to reach?

5) are there hidden reach penalties for certain types of users, or certain types of content? are the rules published and the applications of penalties/boosts apparent?

6) what are they allowed to say? what are they not? are the rules different for different people?

7) who decides when their accounts get suspended? can they be unsuspended? is there an audit trail to make sure policies are applied fairly and consistently, or is it all backroom/hidden?

so what?

People actually believe it, and cause harm.

Case in point: https://www.nytimes.com/2016/12/05/us/pizzagate-comet-ping-p...

So how many people have heard of Pizzagate, and how many of them ended up doing something deranged about it? (The article says no one was hurt, actually, but let's say someone was.) Meanwhile, how many people do deranged things because of beliefs that didn't come from the internet—say, they saw someone looking at them and just knew that person was evil, or they had some misfortune and blamed someone else and decided to get revenge?

I submit that the type of person who believes a wacko theory and kills someone because of it is likely mentally ill, and might well have killed someone because of some other belief; the primary cause is the mental illness, while the specific belief and where it came from is not worth dwelling on.

you are missing the point. with your logic much more should be banned and censored than is.

People also believe WHO and did harm too.

You are walking down a path that doesent lead to anything good.

But it is, assuming you are in the US. That is how the legal framework is laid out. It is extremely difficult and near impossible to restrict speech in public forms.

But then we'd learn about all those oligarchs, abuses of the system, tax evasion, astroturfing, propaganda, opposition gate-keepers, distractions, fake conspiracies etc. ;)