How can a Muslim restrain his tongue from backbiting given its prevalence in gatherings?

Backbiting is forbidden, and refraining from it is within one's capacity, for Allah burdens no soul beyond its capacity. The prevalence of backbiting in gatherings does not nullify its prohibition. Rather, it is incumbent upon anyone present in a gathering where backbiting occurs to forbid it. If the backbiters do not desist, then he must leave the gathering.