It is a famous saying of Lu Xun, which comes from Lu Xun's Self-mockery. It means: "Angry at those heartless people who are accused by thousands of people, bend down and be willing to be the people's willing cows." Never give in to the enemy and be willing to serve the people.
Chinese name
I looked at the condemned man coldly. I bow my head and be a willing ox
translate freely
Never give in to the enemy and be willing to serve the people.
source
Lu Xun's self-mockery