How do I keep TT from excluding all capital gains on the Oklahoma return?

Unfortunately, you must click the "This property does not qualify for exclusion" for each entry.  

You can try to delete the form, but I believe TurboTax will recreate it based on information entered in the federal section.

Windows instructions

1. Open or continue your return.
2. Switch to Forms Mode by selecting the Forms icon.
3. From the menu, select the form you want to remove.
4. After the form is generated in the right pane, select the Delete Form button.
5. Follow any onscreen instructions to remove the form or forms.

Mac instructions

1. Open or continue your return.
2. Switch to Forms Mode by selecting the Forms icon.
3. From the menu, select the form you want to remove (if you don't see it, select Open Form at the top).
4. From the Forms menu, select Remove [form name].
5. Follow any onscreen instructions to remove the form or forms.