Question

Mao Zedong launched the Cultural Revolution in China in response to

Answer 1

Mao Zedong launched the Cultural Revolution in China in response to what he and other Chines viewed as social encroachments from the west that were threatening the Chinese way of life. 

Answer 2

... in response to other persons in leadership in China that Mao thought focused too much on technical expertise and not on ideological purity.

Mao Zedong began the Great Proletarian Cultural Revolution (its official name) in 1966.  A big part of the program was the closing of China's schools, because Mao saw the majority of educators as bourgeois types who were failing to support the communist revolution.  The Cultural Revolution was an insistence on loyalty to communist party ideology.  

The Red Guard was formed, which was made up of high school and college students (no longer attending school, since schools were shut down).  These radicalized students became militants for Mao over against those whom he considered not revolutionary enough.  The Red Guard destroyed historical artifacts and writings of the of China's former culture.  They also attacked persons who were seen to be resisting Chairman Mao's permanent revolution.