His use of deception and violence may be offensive to modern ears, but it’s likely this was not the case for Israelite hearers. Chisholm says that the story appears crafted to appeal to Israel’s disdain for the Moabites. The utter humiliation of greedy, naïve Eglon would make the account of Ehud’s exploits that much sweeter for an ancient Israelite audience that had experienced the oppressive hand of this king for many years.
1
Furthermore, this was holy war; Eglon was an invader in the land, even if he was the Lord’s instrument for punishing Israel. Thus Ehud made war, and in wartime killing, assassination, and deception are proper, assuming the war itself is a just and holy war. What Ehud did was proper in terms of wartime ethics.
2 His act was not any different than Israel’s destruction of the Canaanites in the time of Joshua, and other instances where men carried out divine judgment at God’s own command. Even though the Moabites were the Lord’s instrument for punishing Israel, they still remained His enemies and had no right to occupy His sacred land and oppress His people.
3
21 And Ehud reached with his left hand, took the sword from his right thigh, and thrust it into his belly.