As the head of the Uchiha clan, all dead body is rightfully his to do as he see fit. Too bad it's a couple of days late as Mc could have retrieved some seeds and eggs to store for later.
Since tang san is so agenst the spread of mystic hand cultivation, Mc should spread it far and wide so tang will have to kill half the planet. Mc can also blackmail tang San by creating a nuclear winter bomb if ever Mc family dies.