Why did he say that Ben Hadad seeks evil?
Malbim: The way of war is that when besieging a city, they offer Shalom; if they accept taxes and servitude, they do not despoil the city. I accepted to be his slave, and also the people of my household - why does he seek evil? (a) If he sought only his own benefit, he would not ask for my wives and children 1 ! (b) Since I did not withhold anything from him, why did he add "Li Titen" (verse 5)?
Above (verse 3), Malbim explained that he asked for the good (beautiful) wives! Perhaps he wanted them for himself, or to reward his servants! Ben Hadad did not request only Benosecha, rather, Banecha; perhaps Achav did not fathom that he wants his sons for homosexual relations. (PF)