I got this error when trying to delete a ‘test’ OU called ‘x’ from AD the other day:
“You do not have sufficient privileges to delete ‘OU’, or this object is protected from accidental deletion”
The fix is quite simple, go to ADUC, and under ‘View’ select ‘Advanced Features’. Then right click on the OU you are trying to delete and navigate to the ‘Object’ and then untick ‘Protect object from accidental deletion’ at the bottom. Now you can go back and delete the OU.