One craftsman considered a certain part to be poorly made, and another part to be beautiful. Each overlooked the mistakes that he himself would make, and saw only the shortcomings of the others. But in truth, the whole menorah was made of nothing but mistakes. But if I wanted to, I could have made a menorah that is beautiful. Each of us tends to overlook our own shortcomings, while focusing on the mistakes of others.
Every person has both good and bad qualities.
The son in the story knew this, but he also knew that the craftsmen were in the habit of looking only at the deficiencies of their fellow craftsmen, while seeing their own work as perfect.