It is wrong to ruin someone else's dreams.
Brad is talking to his son, Jay, who wants to be a writer.
Brad wants to impart practical knowledge that will help Jay later in life.
Brad suggests finding a balance between developing art skills, and preforming practical work.
Brad says that Jay isn't clever or interesting enough to be a writer, and if Jay was, would not make any money, and Jay should work in a factory.
Jay listens and learns a valuable lesson in feasibility.
Jay loses self confidence and doesn't develop his passion, and submits to working in a factory while all joy within him dies.