Degrade means to put down––a degrading comment is one that makes the subject feel bad, a degraded field is one whose soil has been worn out. If you move from an A average to a B, you've been degraded.
When you whistle at a passing woman, you're being disrespectful––your behavior is degrading to women. In science, degrade means to break down. Old paper or photographs can degrade when left in the light––their material breaks down so that they crumble at a touch.