It is the government's mercy when a murderer is hanged. That is the injunction in the Manu-saṁhitā. "So parantapa, you are kṣatriya. Your business is to punish the unjust." Kṣudraṁ hṛdaya-daurbalyam: "For a kṣatriya this kind of poor-heartedness, that 'I shall not fight...' Give it up. Don't indulge in such thing."
Then Arjuna replied,
- kathaṁ bhīṣmam ahaṁ saṅkhye
- droṇaṁ ca madhusūdana
- iṣubhiḥ pratiyotsyāmi
- pūjārhāv arisūdana
- (BG 2.4)
He is addressing Kṛṣṇa as arisūdana, the killer of the enemies. He says, "But in my case, I have to fight with Bhīṣma, Droṇācārya. They are my well-wisher, and how can I kill them?