2 Kings 9:6-10: Jehu Punished for Doing As He Was Commanded?

Why is Jehu at first told to carry out the destruction of the house of Ahab and then later on threatened with punishment by the prophet Hosea for doing as he was told (Hos 1:4)?
Jehu was given a twofold divine commission: (1) he was to annihilate all the wicked and apostate house of Ahab, and (2) he was to avenge the blood that Jezebel had shed of the prophets of Yahweh. God's instrument of choice was the army captain, Jehu. These tasks Jehu carried out to the full.

Why then was God displeased with Jehu, as Hosea seems to imply? Because it is one thing to be the instrument God has chosen to punish another person (or group of persons or even a nation) and another to find automatic approval at the completion of the act for the manner in which this task was carried out. For example, Assyria was ordered to move against Israel, but God disapproved of the brutal way Assyria carried out the warfare (Is 10:5-19). Babylon was likewise authorized to move against Judah but was excoriated for cruelty in that war (Hab 1:6; 3:13-16).

Therefore, although Jehu was obedient to God's directive (2 Kings 9:7), he erred grievously in that he killed more people than God had directed and did so with a savagery that did not earn God's approval. It seems clear from Jehu's conduct that he was motivated not by a desire to be obedient to God but by sheer personal ambition--thereby making his act of obedience wicked. It was this same spirit that was transmitted to his descendants, in a heightened degree if anything.

Jehu showed unnecessary cruelty when he slew not only the house of Ahab at Jezreel, but also the visiting monarch from Judah, Ahaziah, and almost all the members of the Davidic family (2 Kings 9:27; 10:13-14). Jehu, furthermore, extended this massacre to all the friends of the ruling family (2 Kings 10:11).

The point is most evident that divine approval for an act does not thereby carry with it indifference as to how that act is accomplished and how many others it may involve.