«وَلَمَّا تَعَامَى الدَّهْرُ وَهُوَ أَبُو الْوَرَى»
When Time itself, the father of mankind, pretended blindness.
Abū Zayd personifies Time as a parent who pretends blindness. He then uses the image to explain why he too feigned blindness. A literary analogy becomes a convenient personal excuse.
Even if society is unjust, that does not logically justify every imitation of injustice. The poem is witty, but wit and a sound moral defense are different measures. The argument belongs to a character who benefits from it.