The Body of Christ

No single person, Christian or otherwise, can consistently, constantly, and consciously further the will of God. However, within a given number of people, like the Church, there will always be someone committing Christian acts which further God's will. It is the totality of these assmbled acts that constitute the "Body of Christ"--a single manifestation (though spiritual, not physical) with a single purpose, just as our bodies are a physical entity with a single purpose.
To threaten someone's body is to threaten their physical existence. It would stand to reason, then, that sin threatens the "Body of Christ's" existence. Sin is a cancer to the Body, and must eventually be excised in order to preserve the Body.
This explains the end of times. The end of days will come when man reaches the point of corruption when God must perform "surgery." Satan's plan is to corrupt man so fast and so thoroughly that the Body will die before the cancer can be removed. God won't let that happen, of course, but that explains why sin hurts him so and why we should work so hard to excise sin from our life, so that we may become more solidly a part of the Body of Christ.