Quote from : Why Does He Do That?: Inside the Minds of Angry and Controlling Men Book

Objectification is a critical reason why an abuser tends to get worse over time. As his conscience adapts to one level of cruelty—or violence—he builds to the next. By depersonalizing his partner, the abuser protects himself from the natural human emotions of guilt and empathy, so that he can sleep at night with a clear conscience. He distances himself so far from her humanity that her feelings no longer count, or simply cease to exist. These walls tend to grow over time, so that after a few years in a relationship my clients can reach a point where they feel no more guilt over degrading or threatening their partners than you or I would feel after angrily kicking a stone in the driveway.