What is the ruling regarding accusations of drinking alcohol and the like, and what should one do if unable to leave a gathering where such talk is frequently repeated?

In Islamic legal terminology, "qadhf" (accusation) is limited to accusing someone ofzina (unlawful sexual intercourse). If someone accuses another of drinking alcohol, they are not considered a "qadhif," even if they are sinful. Accusing an open alcohol drinker of their act is not considered backbiting (ghiba). However, if the person conceals their sin, then they should be advised and their sin should be covered, and they should not be exposed unless there is a benefit in doing so. Sitting with someone who is backbiting requires enjoining them to stop. If that is not possible, then one should leave the gathering. If that is not feasible, then one should condemn it in their heart.