Why were so many answers defaced by replacing the text with:
(Answer not available under cc by-sa 4.0)
for example: https://workplace.stackexchange.com/a/140306/7777
Stack Exchange changed the license in September.
That would be fine, when all posts previously written and granted rights to SE by users had stayed with their old license. But they did not. SE decided that the licence you granted them is not the license they wanted and decided that meant that you had indeed granted them a different license. Just for comparison, that is exactly what happens when you pirate a movie. You decide unilaterally that the license offered (pay for view, copying not allowed) does not suit you and instead use your own license (free to view and copy) without the consent of the other party.
Now, the real problem is not the license change per se because people agree it is for the better, but instead the fact that SE decided they could decide for us that we agreed to this. There was not even an opt-out. Not even saying "if you don't agree we will have to delete your content". Just "my way or the highway". That upset many users.
I don't have time to look it up, but if Gregory removes their answers older than September, then they actually have a point... legally, they are not available under the current license. Unlike posts written after September, Gregory never agreed to it being published under the new license.
You could argue that that should be taken to court instead of doing it manually by editing and maybe that's correct.
TL;DR Let's, for once, prioritise individual contributors over the collective.
Our interests, as a community, are different from the direction SE is taking. It's just the way things are going in the last few months. SE Corp's interest is to protect the content. It stays on their site and google results. Individuals come and go. SE gets contributions for free, and that's fine, because community feedback was taken into account, up until recently. SE can and will "burn" long-standing members in order to pave their new path.
For some reason I still use facebook. Sometimes, I get a "disturbing" picture in my feed that I have to click to reveal. To me, Gregory's action is similar to that. The answer is there if you want it, beware of the licensing issue.
At the same time it's raising awareness of this issue. You can't just relicense stuff. That's not how it works.
It's easy to say "two wrongs don't make a right", and I would agree with that if it weren't for the power imbalance between SE Corp. and regular contributors. You're already getting our content for free, which we're happy to provide.
Similarly, someone mentioned this vandalism ruins the experience of others on the site. I agree with that. We should also consider the experience of strong contributors, like Gregory, who writes insightful posts we enjoy, and SE decided - unilaterally - to re-license.
SE is turning strongly corporate, abandoning its grassroots base, since it doesn't really need it anymore; it has enough momentum, and Google presence, to keep going. That's fine. They're a company, they're in it for money, and it makes sense they would do this at some point. But again, you can't change the license without agreement.
Please don't penalise Gregory for SE's nonesense. If you do we might lose him and other valuable contributors.
Gregory should not delete his answers. Stack Exchange has a reputation system central to the way it works. Experienced users may not realise this, but for new contributors it's a big deal. Deleting an answer removes the internet points. So what, I hear you ask, who cares about Internet points? Contributors do. Yes, they're meaningless. I can't go to the bank and put 10k rep as collateral. But I earned them, goddamnit, and the only way you can take them away is from my cold, dead hands.
I'm joking of course, exaggerating a bit for comedic effect. But you get the point. Plus, earning rep points is a "gateway drug" to a SE community. So, it's important.
I sympathize with the point of view regarding the Creative Commons licensing change, but legal issues are not the responsibility of the volunteer moderator team.
Please take issues like this up with the Stack Exchange company instead, as others have, and if you do have the legal right to remove your content from the network, they can do it for you.
I've reviewed the edit logs Gregory's top 10 answers by votes and it clearly appears that he no longer wishes for his answers to be available under the current license regardless of internet points. He has made every effort to delete his answers as is permissible to him as a user by actually deleting the answer; he could not delete accepted answers and simply removed them with the cited statement above.
As the information is his creation and subject to the copyrights that he agrees to, I do not understand why the moderation team is working to undo the deletions and edits. This very much appears to be an infringement upon Gregory's copyright and I do not concur with the rollbacks that have occurred given that the community does not appear to have a consensus on the matter.
Any person who rollbacks such edit is a partner in copyright infringement with Stack Exchange.
Before rolling back such an edit make sure you know the support that SE is willing to give you in the unlikely event that you get sued by the original poster for copyright infringement. Same applies to undeletion of answers or questions.
Some may disagree, of course. But why take risks for an organization unless such organization has ensured that it would support you in such an event?
Update: I made a test. I added a license statement to my oldest answer which was posted before Sept 5 2019, when SE changed to CC-BY-SA 4.0. The license statement was rolled back by a moderator with the following edit message:
Please leave the license stuff off. If your not happy about that, please use the contact us link at the bottom of the page as this issue is above the site mod's pay grade.
I agree entirely about "this issue is above the site mod's pay grade". Though I wonder why they act on it if it is indeed above such pay grade. It seems it is above but only in one direction.
The moderators are still responsible for their actions though. "SE told me to do it" is no valid excuse for copyright infringement.
If I were to take a guess, my assumption would be along the same lines as the answer above https://workplace.meta.stackexchange.com/a/6494/113825.
It's likely that Gregory wanted to delete his answers, however was unable to as they are "accepted".
Also, I believe there is a limit to how many questions you can delete per day and maybe he hit that limit.
It's possible that Gregory contacted the CM team to ask that his content be deleted, but they were not accommodating.
It is hard to tell.