The text on the paper the worker is holding:
Highest instruction. We must fight with literary means, we must not fight with military means!
(最高指示. 要用文斗，不用武斗! - Zuigao zhishi. Yao yong wen dou, buyong wu dou!)
This instruction was part of the 'Sixteen Points' on how the Cultural Revolution had to be waged, issued by the Party in August 1966.