Arjuna refuses to fight. Lord Krishna tells Arjuna that he will be taunted, and asks if Arjuna can face up to that. A yogi is not bothered by taunts. But Arjuna is an ordinary mortal. A story is told of sage Suka, which shows how yogis sometimes seem eccentric, and yet are treated with respect, said Valayapet Ramachariar, in a discourse. There was a king, who was generous in providing food to others. The food was served on plantain leaves, and the used leaves were counted, to know how many people had been served. Every time a thousand leaves had been counted a bell would be rung, to indicate the number of people who had eaten.
One day the bell sounded, indicating a count of thousand. But it was found that the only person eating was Suka, and he was eating leftovers on a leaf. He was such a great yogi, that his eating a few leftovers was enough to confer on the king the merit of providing food to thousand people. But Arjuna is no such yogi.
Arjuna, as a king, has a duty to protect his subjects. If he dies fighting, he will attain moksha. A warrior cannot shy away from a war. Can a lion be meek like a deer? Krishna gives a long preamble in the Bhagavad Gita before He starts talking about the paths to moksha like Karma yoga etc. Doing one’s duty is easier than other paths to moksha. If one resorts to penance, and gives up halfway through, then all the benefits accumulated until then will be lost, and one has to begin all over again. Every time Viswamitra broke his penance, he had to start from the beginning. But if one resorts to Karma yoga, and then gives up after sometime, then one reaps the benefits for what one has done. Those benefits are not lost.