When one recalls the Interchange of Love with the Father vs the nervous system’s perception of outer change, there is no chance for fight or flight to kick in (and cause trouble in the Sonship).
Every non-loving thought about a brother becomes a barrier to Knowing the Father’s Love, and every loving thought about a brother re-opens the door to Knowledge of Oneness. Fight or flight is an aspect of giving reality to the “detour into fear” (ACIM) — the fight or flight response to a brother is never Known to be appropriate in Truth. Only the normal state of Mind that ever acknowledges the Father’s Love for His One Son is appropriate. There is no violence in this state of Mind whatsoever, it is absolute Love in continuous climax with absolute Love.
Jesus Knew, and taught by example as he went willingly to the cross, the inappropriateness of extending fight or flight.