You have to make sure the Everyone group has View Objects right granted on the users top level:
CMC > Users and Groups > Manage > top-level security
Select the Everyone group > assign security
Go to the Advanced tab > add/remove rights
Scroll down to "View Objects" right and grant it. Uncheck the last column on the right so it doesn't get distributed to sub-objects
With that setting, you have access to the top-level of users list, and your user will only be able to see the users it's allowed to see.
Frederique
