Censorship is required if one wants to prevent libel and slander. There are some people who won't stop doing it unless an entity with more authority/power stops them from saying it.
I've always been of the mind that I'd rather let 10 guilty people walk free than imprison one innocent person. I extend that to free speech as well. I'd rather let 10 lible or slander complaints work their way through the court system rather than wrongfully censoring one person's speech.
This mechanisms formed in the email network long before the current oligopoly formed, and still works.
So I hope there is a honest way to filter out generally objectionable content by.a collective effort of the users who care, without turning the filter into a censorship tool.
But you can always create a new identity that does not trust the other person — or set your own local trust — to see the content anyway.
The important point is that this way resistence against disruption of communication scales better that the disruption (spam, libel, harassment, ...).