false positives for read-only custom textfields

Greetings,

I have a custom field for storing congressional districts set up to be
a read only textfield. When I mark the field as a 'selector field'
and click on a CD value in a profile, the resulting listing returns
all the contacts in the database rather than the contacts with the
same CD value.

When I uncheck the 'Read only' box
when setting up the field in a profile, it works properly. However, I
want the box to be read only and have my accompanying drupal code
modify the contact's CD based on the contact's address.

REPRODUCING
–
This is how I reproduced the bug on http://demo.civicrm.org/drupal :

I created a custom data group called 'read-only selector test'. In it, I created a single, searchable alpha-numeric field called 'CD'.

Then I when into the 'Personal Info' profile and added the field, setting it as 'View Only', for 'public user pages and listings', 'In Selector', and making it 'searchable'. I then edited the profile for several users (including the demo user) to have 'XYZ' as the value for this field. Then I went to the demo user's drupal profile page: http://demo.civicrm.org/drupal/user/2

There, I clicked the 'XYZ' values for the CD field so I could see a CiviCRM generated listing of all the other users who have 'XYZ' as the value for their CD field, but the listing returned all the contacts in the system. Unchecking 'View Only' for the field makes it work correctly. But for the project I'm working on for a client, we really need the field to be a selector field while being 'View Only'.