Let me define "unacceptable damage" for you. Unacceptable damage is when China unleashes its thermonuclear arsenal and wipes out every Indian on the subcontinent. That's unacceptable damage.
China only needs a single Indian ballistic missile headed towards a Chinese city to declare "escalation" by India. American and Russian satellites can verify the Indian ballistic missile trajectory. Once India escalates, China will retaliate with hundreds of megatons. Indians just became extinct.
You cannot bring one megaton to a 294 megaton fight. Only an idiot would think otherwise.