Psalms is a book about faith, but that doesn't mean there won't be a fight over it. The Israelites of old lived in a rough neighborhood, and victory or defeat often meant enslavement, death, and the demise of your entire culture. Israelites lived next door to people getting massacred left, right, and center. In Psalms, they talk about their enemies as part-human cannibals who would stop at nothing to force idols on the Israelites.
In Psalms, God also makes a habit of completely annihilating his enemies. We're talking The War of the Worlds style. And if you're loyal to God, you earn the right to use his powers to wipe your enemies off the face of the earth.