I don't get it.

If the offense was posting a defamatory message, then why worry about deleting the message?  The damage was done when that member posted the message, years ago.

It seems to me that if the messages were the problem, perhaps the member should have been put on moderation or deleted for posting the message, not for deleting it years later.

Do you suggest you have a responsibility to defend that member if someone sues him?

Andy