I should have mentioned...I did try using clear-goals, that was actually my plan to begin with. But as these are every-time sexps (because there will be multiple waves of red wing), using clear-goals then add-goal just makes Beta wing fly in tiny circles, confused, as their goals get repeatedly voided out and re-added.
EDIT
Additionally, I tried having Red Wing protected until they get 10,000 meters from the cap ship, but this doesn't work either, because the unprotect-ship sexp only lets you select individual ships, not wings. Which sucks, because there's many waves of Red wing to be had...