Wikipedia is open to publishing defamatory content as it allows editors too much free reign to edit according to their own prejudices. Even one of its founders said it was no longer a reliable resource. It's good for looking up pop stars birthdays and how much a camel weighs but untrustworthy on anything serious. I'm surprised they haven't been sued before.
All sources should be subject to
“Extraordinary claims require extraordinary evidence”. I personally think Wikipedia has a sensible approach. Whilst anybody (pretty well) can make any edits, there is a system of scrutiny and protections. For most casual editors/contributors all edits they make are put in a list requiring "patroller" (admin/moderator) scrutiny. Whilst those edits will go live immediately they are in a list to be scrutinised by a "patroller" who can revert them and this reverting does happen and it's quite strict and the contributor might not notice their edit has been reverted (eg is made anonymously).
Often a revert (undoing an edit) can be for minor things like no citation - add a "fact" and in many situations a reliable source for the claim is required to be quoted as part of the edit.
Some pages are placed on additional scrutiny/protection whereby you have to have made a good number of edits before you can edit the given page eg pages about political figures or controversial events, etc. ie those more subject to mis-information.
Once you have made a good number of approved/patrolled edits as a registered user you can be set to "auto-patrolled" meaning edits you make are not put in the normal scrutiny list as you've proved yourself as reliable (ie your edits are automatically approved). I can't remember what the typical threshold number of edits before becoming auto-patrolled is but I've total about 16,000 Wikimedia edits and am auto-patrolled on 3 of the projects (incl. Wikipedia).
Ian