Sadly, you can make as many rules/guidelines as you want but, human nature being what it is, you will never get 100% adherence to those rules and guidelines.
I'm trying to figure out a way to minimize honest frustration (and sometimes malicious backlash) of users whose posts got deleted.
We'll always have to delete/lock posts no matter what guidelines we adopt. Also, most of the time things are not black or white, so the moderators need to make judgment calls.
That means there will always be users upset about something.