Is a person sinful for listening to backbiting while hating it in his heart and being unable to advise those who backbite for fear of their anger, all the while trying to leave the gathering if possible?

A Muslim must denounce evil when they witness it, as the Prophet, peace and blessings be upon him, said: "Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart—and that is the weakest of faith." Forbidding evil is an obligation that is not waived except out of fear of severe harm that exceeds or equals the evil itself. Mere anger, cursing, or insults from the one being denounced are not an excuse for not denouncing. Disliking it in one's heart is not enough if one is capable of denouncing it with their tongue. If the evil does not change after denunciation, then one must leave the place, as Allah Almighty says: "And He has already revealed to you in the Book that when you hear the verses of Allah being denied and ridiculed, do not sit with them until they engage in another conversation. Indeed, in that case, you would be like them." Sitting in a gathering of sin without denouncing it is considered an approval of it, and one who approves of a sin is like one who commits it.