I see firing in such a case as a cop-out, a cowardly way to appease mob-mentality.
In this case if the employee responsible for firing the moderator did such acts repeatedly despite management warnings than perhaps it's a good idea to fire that person. However this doesn't seem to be the case, the CTO correctly assumed responsibility in his apology of green-lighting the moderator's firing.
He does the right thing, in my opinion, by promising a better process that wouldn't lead to such a hurtful (and seemingly unfair) dismissal.
You don't fire an employee for mistakenly deleting your production database, you update your process so this cannot happen (at least not by accident).
In this case if the employee responsible for firing the moderator did such acts repeatedly despite management warnings than perhaps it's a good idea to fire that person. However this doesn't seem to be the case, the CTO correctly assumed responsibility in his apology of green-lighting the moderator's firing.
He does the right thing, in my opinion, by promising a better process that wouldn't lead to such a hurtful (and seemingly unfair) dismissal.
You don't fire an employee for mistakenly deleting your production database, you update your process so this cannot happen (at least not by accident).