Why does the Watchtower use the word 'apostate' to label everyone who leaves their organization? No one can be sure, however the Watchtower seems to understand how name-calling can be an effective tool.
According to the Watchtower, 'Name-calling slaps a negative, easy-to-remember label onto a person, a group, or an idea. The name-caller hopes that the label will stick. If people reject the person or the idea on the basis of the negative label instead of weighing the evidence for themselves, the name-caller's strategy has worked.' -- See Awake!, June 22, 2000 pages 6 - 10 See Why Do Jehovah's Witnesses Fear Apostates
Some critics say that name-calling and labeling disfellowshipped Jehovah's Witnesses is a Theocratic Warfare strategy designed to emotionally harm those who leave and Jehovah's Witnesses in good standing with the organization. Families and close life long friendships are destroyed in order to prevent members from finding out the truth about their religion. They say that Theocratic War protects the organization from harm at the expense of individual Jehovah's Witnesses.
Watchtower literature has also encouraged readers to hate apostates. Christians know that hatred of enemies violates the teachings of Jesus. Hatred in any form and for any reason is not Christian. Jesus taught us to love our enemies. He even blessed and forgave his executioners who ridiculed, tormented, and tortured him as he suffered a horrible, painful death. Matt 5: 44 - 47; Luke 23:33,34.