Is a person considered to have apostatized if they smile at someone who insults the faith, and what should they do?

The listener of one who curses the religion does not share in the speaker's disbelief unless he approves of it. The listener's duty is to denounce the speaker. If the listener laughs in agreement and encouragement of the speaker, he must repent and pronounce the two testimonies of faith. However, if his laughter is without agreement, he must seek forgiveness for failing to denounce.