If a space where a community gathers isn't trusted, core members of that community are going to want to leave.
Trust is delicate. Trust is giving someone the power to do harm you or to misuse what you have given them, in the belief that they will not do those things.
The trust has been shattered, and probably only the core members currently realise this. Those are the users for whom "this is our voice, this is what we've said" is important.
It is really sad that the trust has been broken, but there you have it. If key people in any community believe that their words (which are their reputation) can (will) be edited, misrepresented... then there really is a problem.
The worst-case logical conclusions are legal liability, the best case is stress and friction caused by confusions and mis-truths.
I run forums, I know this is about trust, I've seen it played out.
When I designed the forum software for the sites I run I made the database an append-on-write system to store historical revisions of every comment. I can't display those (if a user edited something to remove something that had legal/personal implications then they should not be public) but I do store them and provide no moderator any access to edit them.
Trust is really important. This isn't, as others suggest, petty.