The last text before Mao begins turning to communism is a fascinating series of comments on Friedrich Paulsen’s A System of Ethics. On the question of evil. Mao disagrees with Paulsen and writes:

We should emphasise only whether or not the reality at the time was good or evil. If the actual activity is good then it is good, if evil then it is evil. We should not think about being good in order to leave behind a good historical reputation or about evil leaving behind a bad reputation historically. When we judge history and say that someone was good or that someone was bad, we are referring to the good and bad actions of that person. There is no goodness or evil apart from real actions. Thus it is stupid to think of leaving behind a reputation for all time, and it is also stupid to envy the reputation that others may leave behind them.
If disease inspires the medical arts and teaches a sense of patience and benevolence, if suffering is able to move the heart and instil patience, if falsehood is conquered by truth, if evil thoughts submit to one’s conscience, is this not precisely because they are evil? … The reason we cannot do without evil is that it is capable of assisting our resistance and struggle, and thus every kind of evil is always under attack and being suppressed; it is not just that it is inevitable.
We want to do away with evil because it is enemy to the fulfilment of life. Thus we eliminate evil in the process of fulfilling life, not just to eliminate evil. In wishing to live a full life, how am I to know whether the evils are many or few or whether I shall eliminate them or not.
Revolutionary Writings 1912-1949, vol. 1, pp. 241-43.