The verse highlights Arjuna’s confusion by the choice of names he uses to address Krsna. Janardana means protector of people while Kesava means killer of the demon Kesi. Arjuna is not sure whether Krsna is protector or destroyer. In fact He is both – protector of good and destroyer of evil.
Action by itself is neither good nor bad. It is the intention, motive, that determines the quality of action. The same action could be good if driven by a desire to do good and could be gruesome if motivated by a negative desire.
Arjuna is confused because Krsna has elaborated on the importance of knowledge in Chapter 2 yet encourages Arjuna to fight. Arjuna is faced with the prospect of having to fight and kill his own beloved patriarch, Bhisma, and Dronacarya, his guru who taught him archery. He cannot understand how Krsna could ask him to perform such a repulsive action. Arjuna has lost sight of the purpose of the battle which is to restore righteousness. Bhisma and Drona, though noble, happen to be on the wrong side. Arjuna needs to focus on the larger picture rather than get caught up with his personal relationships.
Besides, Arjuna is a warrior. His duty is to uphold virtue and justice. He has fallen into a temporary sense of false renunciation where he wants to give up the kingdom because it is painful to fight.
The Bhagavad Gita is open to questioning. It is not a text of dogma and instructions. You can only live by your own conviction. You cannot live a master’s vision, however right it may be. When the student asks questions it indicates his desire to learn and receive knowledge. He is not content to merely learn by hindsight. He is conscious of a higher purpose in life, the state of Immortality. If you even mildly accept the notion of eternity it becomes real for you, yours to pursue and attain. Then you leave behind the belief that you cannot change and the activity that supported that belief.