First of all, Zhu Ziqing did not starve to death, but died of illness, due to a severe stomach perforation caused by overeating.
Secondly, as a professor, Zhu Ziqing did not lack food. His call to not accept relief grain is a typical case of moral blackmail, standing aloof and losing humanity for political purposes.
Thirdly, Zhu Ziqing's son was executed by firing squad in 1951, getting what he deserved.