Are the backbiter and the one who did not object to him equal in the obligation to seek forgiveness from the backbited person?

The Shariah prohibits sitting in gatherings where evil acts like backbiting occur. Therefore, whoever sits in such gatherings without condemning them is either a participant and approves of them, which necessitates seeking forgiveness from the wronged party, or he disapproves in his heart but does not voice his disapproval. In this case, he has committed the sin of remaining silent about an evil act, and he must repent and seek forgiveness for the one who was backbitten. He is not required to inform the wronged party of what was said about him.