How can one differentiate between ridiculing Islam and an unintentional mistake, and what is the ruling if a person laughs or smiles upon seeing or hearing something of that nature which they cannot resist, and is this laughter considered ridicule of the religion?

Mocking the religion is an act of disbelief (kufr) that expels one from the fold of Islam. It encompasses every word or action that indicates slandering, belittling, or treating the religion with contempt. A Muslim must vehemently condemn mockery of the religion and leave the place if the mocker does not desist. Smiling and laughing when the religion is being mocked makes the person a partner in sin if it is out of approval, and it is a major disobedience if it is not out of approval.