事不可使親痛仇快 to sadden one's own people and gladden the enemy

Yi Junqing-Chang Yan scandal reminds me of another guy, who is a vice-president of a university in China now.

One should not do things to sadden one's own people and gladden the enemy

Besides experiences that based on the result of hundreds thousands of death, Mao wrote "On Practice" to response Wang Ming, partially. To motivate myself I also should imagine a competitor. This is reality that if one is not smart enough, he could "waste inside the cage".