It definitely desensitizes JWs to tragedy. I remember talking with an elder right after 9/11, just to get his thoughts on it. His exact words: "It's 3000 people who wouldn't have survived Armageddon anyway."
And their dehumanizing of 'worldly' people is what makes the notion of God wiping out 6 billion people palatable. It allows them to disconnect from the reality of the level of death and destruction.