As Yaakov and his family are leaving Lavan’s estate, Rachel steals the תרפים of her father. The definition of תרפים is somewhat unclear, but Rashi explains that these were some sort of idols, and Rachel acted to prevent her father from idol worship. Interestingly, Rabbeinu Channanel (as well as the Rabbeinu Bachaye) states that Rachel’s intent was to demonstrate to Lavan the absurdity of this kind of idol worship. If Teraphim have no ability guard themselves, they clearly have no power.
This, cites Rabbeinu Channanel, is the story of Yoash, the father of Gidon. A Malach came to Gidon to initiate him as the judge who would battle Midyan. He was instructed him to go and destroy the altar of the Baal – which he did. The next day the townspeople came to Yoash, demanding he hand over his son, so they could kill him.
Yoash answered האתם תריבון לבעל – you’re going to defend the Baal? You’re going to fight his fight? Let him fight his own fight!
Rabbeinu Channanel explains: Yoash had figured it out overnight. Once Gidon had destroyed it, Yoash realised the Baal was worthless and meaningless.
We see from this that there are two levels:
1) To prevent someone from doing an Aveirah.
2) To demonstrate to them why the Aveirah is futile, and is indeed against his best interests.
Shabbat Shalom