Ostensibly, he revered Baal, expressing a pious theological view on the idol: Baal did not require human action to protect him; he could fight for himself. This does not mean that Joash really supposed that Baal could or would do so. It was just a tactic to prevent the villagers from killing Gideon. Joash may have sympathized with his son’s action. He may even have had some half-hearted reverence for Yahweh; all while being a Baal worshipper in public along with the village.
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.”