My church's advent sermon series is an unconventional This is War. The premise is that Jesus' birth was an invasion in God's war on Satan, sin, and death, and we need to remember that we are at war with those things.
This is not a new idea; John Eldredge talked about Christ's birth as an invasion in Waking the Dead. Eldredge agrees that Satan is a enemy we must be aware of. However, he argues that the war is not on Satan, sin, and death, but rather a war for our hearts (Waking the Dead).
Now there is also substantial analysis about whether Satan is an actual being versus a metaphorical term to describe those in opposition to ourselves. Misunderstandings of the Fall, Hell, and Satan can definitely affect our views of spiritual warfare (summary version: most of our ideas of Hell and Satan come from John Milton's Paradise Lost, and we read those ideas back into the Bible).
Regardless, I agree that spiritual warfare exists, be it between literal dueling angels and demons or metaphorical angels and demons.
What I do not believe is that it is a war on sin. As I discussed in my review of The Pursuit of Holiness, the overemphasis on sin is a misrepresentation of the holiness movement. And it gives sin too much power. It also depends on how sin is defined. Really, anything disrupting the relationship between God and humans and God is sin, but more often, the functional definition of sin is misbehavior, which is very much limited. If and when sin is used in the former sense, it could be a war on sin, but as it is used in the latter sense more often, that is how it is defined here.
Does God hate sin? Yes. Is God's main focus sin? No. Can God tolerate sin? Well, he did when he spent 33 years amongst sinners.
Jesus' words did not focus primarily on sin. They focused on love. Remember the Greatest Commandment? It's all about loving God and others; not about avoiding sin. As my wife said after the message this past Sunday, focusing on the removal of sin just treats the symptom, but not the cause. The core problem is not sin. It is separation from God (yes, sin has a part of that, but it's not the whole thing). The only thing that mends a relationship is love. The solution to sin is not spiritual disciplines. It is love--loving God, others, and ourselves.
After the message, we sang Hillsong's Tear Down These Walls to emphasize solidarity in being at war together. Ironically, there is no mention of sin. Rather, they key phrase is "Let love tear down these walls." We need to emphasize love and hope, not the avoidance of sin and death.
In John 10:10, Jesus asserts, "The thief comes only to steal and kill and destroy; I have come that they may have life, and have it to the full" or "I came that they may have life, and have it abundantly." Focusing our energies on sin and death usually make us feel dead and destroyed. Emphasizing the love and hope Christ gives us helps us remember that we, indeed, do have life and that sin and Satan have no power over us when in Christ.
In contrast to the Sunday messages, this past Monday we had a leaders' meeting. The theme was still spiritual warfare, but it emphasized the power of change and hope. The emphasis was on the power of love and prayer. Rather than only discussing what to avoid and fight against, I find it so much more powerful and important and effective to really preach what we are to do and to fight for. And the answer is love.