The English Wikipedia is a massive target for influence campaigns. I don't think there are any other communities as resilient as it. Just an example: There's certain individual or group that edited under the name "Icewhiz", was banned, and now operates endless sockpuppet accounts in the topic area to influence Wikipedia's coverage on the Middle East. One of them was an account named "Eostrix", that spent years making…
The non-profit public benefit service they provide is the openly editable encyclopaedia wiki, not its contents or its editors. The same safe harbour provisions as with other content hosters should (and need to) apply as with YouTube hosting questionable videos.