What does Proverbs 12:1 mean?

Life is filled with trial and error. Most people learn from their mistakes. A bruised knee is adequate motivation for a child learning to ride a bicycle. He gains the desire to practice more, so he can balance properly. A student learns from mistakes in homework assignments and exams what is wrong and what is right. A child receives correction from a parent for misbehaving, and he changes the misbehavior. Everyone faces a learning process when starting a new job, learning what performance is acceptable. He goes on to correct what is unacceptable and to do what is expected.

Those are all natural and beneficial ways of responding to the "discipline" implied here by Solomon. A wise person takes correction and criticism under consideration. The contrast to this is the one who refuses to hear those corrections. Such a reaction marks the person as "stupid." The term used here implies someone with an animal's uncontrolled and simplistic mind. Those who refuse to be corrected are like unreasoning animals (2 Peter 2:12). They may be highly intelligent, and well-educated, but the person who refuses to be corrected is inarguably "stupid," in that sense.

The use of the terms "love" and "hate" here must be understood in their ancient contexts. Solomon is not primarily speaking about emotions. Rather, this implies an extreme contrast between preferences. The point is not that godly people "enjoy" being corrected. Rather, it's that they welcome constructive criticism and seek to apply it. Those who ignore those lessons have chosen to "hate" them and are acting stupidly.