Chinese police detained a well-known Marxist at a top university on Wednesday, a witness said, on the sensitive anniversary of the 125th birthday of the founder of modern China, Mao Zedong, whose legacy remains deeply contested. Qiu Zhanxuan, head of the Peking University Marxist Society, was grabbed and forced into a black car outside the east gate of Peking University by a group of heavy-set men who identified themselves as police, a student told Reuters.