daf bit: Avodah Zarah 52

An idolater can annul an idol belonging to himself or to another idolater, the mishna says, but an Israelite cannot annul an idol belonging to an idolater. How does he annul it? If he cut off the tip of its ear, nose, or finger, or if he defaced it, then even if no material was lost (nothing was broken off), it is annulled. But if he spat before it, urinated before it, dragged it in the dust, or hurled excrement at it, it is not annulled. If he sold or gave it as a pledge, Rabbi says he has annulled it but the sages say he hasn't. (52b-53a)

The forms of annulling that work involve permanent changes to the idol, so it makes sense to me that they would make it no longer suitable as an idol. An implication of that reasoning is that idols can't be repaired; I don't know if the rabbis actually say that somewhere. (Not here.) The second list are all things we consider disrespectful but that don't physically alter the idol; apparently any spiritual damage they do is not permanent. Also, we're told elsewhere that some idols are actually properly worshipped with human waste. (I am not making this up.) So there's that.