He means that we must not follow books but learn from them and find our path in the concrete world.
Marx thought peasants were reactionary by definition. Mao leaned Marxist theory, but instead of worshipping Marx, he analysed China economic social formation and saw the revolutionary potential in china's peasants. We must learn from Mao, but not worship him.
But as today was a machine they listened, because nowadays we trust AI more than people.