In studying any topic, including spiritual warfare, we need to deal with the full range of biblical material on that topic. We must not ignore or gloss over passages that are difficult to understand or that appear contradictory. For example, the softball team captain I encountered twelve years ago thought evil spirits were lurking everywhere, even around second base. These relevant passages must not be ignored in any consideration of spiritual warfare. Teaching on this topic must deal with the full teaching of the Bible or it will be seriously inadequate.
Oversimplification results in distortion of biblical teaching.
Second, oversimplification results in a shallow understanding of the nature of sin. The Bible offers several models for understanding sin. The one presented most often in teaching about spiritual warfare is based satanic temptation. This model uses the example of Adam and Eve's failure and Christ's victory. Undoubtedly, many people are tempted by Satan and find this model helpful, but this is not the only, or even the dominant, model in Scripture.