It is bullying and intimidation. In reality, however preeminent he may be in the village, Joash would never be able to accomplish what he said; he was bragging. The added sense of urgency—“by morning”—heightens the bragging to the point of madness. As his fellow villagers intimidated him, he in turn intimidated them. Inside, he may have been nervous and anxious under their threat.
31 But Joash said to all who stood against him, “Will you contend for Baal? Or will you save him? Whoever contends for him shall be put to death by morning. If he is a god, let him contend for himself, because his altar has been broken down.”