Was Aeneas justified in killing Turnus in the Aeneid?

Throughout the Aeneid Aeneas follows the will of the Gods (which is also Fate). Aeneas is fated to kill Turnus, so that the Roman race can establish itself in Italy.

It is Aeneas' duty to follow his destiny, since resisting destiny is to resist the will of the gods.

Vergil in many ways has ideas which closely anticipate the thinking of the Christians who would arrive a few generations later. The idea of submitting one's personal desires to the will of god is very Christian. (Aeneas does it by leaving Dido, Christ did it in the Garden of Gethsemane).