1. The western tribes confront the eastern tribes about the altar they built, right after parting peacefully from them. Zeal for God's glory motivates the confrontation. If there is rebellion against God, there will be disturbance, conflict, even battle.
2. The western tribes go not only to confront, but to bring peace. They attempt reconciliation, before swooping down and attacking. They inquire before invading. They offer some of their own land, if the land is a problem. This combines truth with love (Ephesians 4:15), as Jesus did with us. His first coming was for reconciliation, when He spoke truth and judged us, but also gives plenty opportunity to repent. His second coming will be in judgment.
3. The eastern tribes' defense appeals to god's name. Don't spare us if we have betrayed God, but we haven't.
It is good for others to check up on you, even to question you. Needs to be done and received with love and truth.