In what ways did Communist ideas differ from those of Confucian China?
For a long time in Communist China, Confucius and his ideas were scorned and rejected. There are a number of reasons for this.
First of all, Confucianism is a very traditional way of thinking. It strongly emphasized the idea of filial piety in which people revered those set above them. The Communists saw this as an ideology that encouraged feudalism and archaic ways. For this reason, they rejected Confucianism.
Second, a major aspect of Confucianism was the idea that the government owed a duty to the people. Confucianism stressed that the people had to obey their rulers, but only when the rulers did right by the people. As the "salem-history" link says,
Confucius’s approach to government stressed that the ruler should be benevolent and sincerely concerned about the well-being of his subjects. In Confucius’s hierarchical conception of the social order, the ruler’s concern for his subjects would be repaid by obedience and support.
This did not fit with the Communists' demands for unconditional obedience from their subjects.
For these reasons, the Communists tried to play down the traditional Chinese reverence for Confucius and his ideas.