To get the economy back on track, China is trying to champion its domestic companies and reassure entrepreneurs that it’s ready for business.

Its efforts are running into a problem: an online army of Chinese nationalists who have taken it upon themselves to punish perceived insults to the country — including from some of China’s leading business figures.

In recent weeks, bloggers who usually rail against the United States have turned on China’s richest man, calling him unpatriotic, and encouraged boycotts that have wiped out billions from his beverage company’s market value. When fellow tycoons defended him, they were attacked as well, by users whose profiles featured photos of the Chinese flag.