You can build a query to display the constituents who have opted out of emails. Navigate to:
  1. Data Management, Query
  2. Create New Query
  3. Enter Name and Description
  4. Field Type: select Email
  5. Field: select Accept Email
  6. Click Add Field Clause
  7. Set "Accepts Email" to equal False
  8. Click Save
  9. Click Add Group Clause
  10. Search for the Group in question
  11. Click Save
  12. Click Save Query
  13. Click Run Query
This will give you a list of the constituents in the group that have opted out of email. You can view your results in the Results tab.