All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
In fact, even if it is proven that a Muslim has committed a disgraceful act, then in principle, the misdeed is to be concealed, and he is not be exposed for no certain benefit. In addition, if a Muslim is entrusted with a secret, it is impermissible to disclose it.
Non-adherence to such religious limits and rules leads to a state of disorder, incurs Fitnah (tribulation) and severs relations between people. Your current situation is evidence of this. Hence, it is incumbent on all of you to turn back to Allaah, the Exalted, in repentance. The conditions of repentance have been underlined in Fatwa 86527.
Moreover, everyone who this man knows was involved in false speech concerning his honor should seek pardon from him; however, those who libeled him and he did not know of it should supplicate Allaah on his behalf because informing him of that often incurs harm.
On the other hand, you should strive to reconcile because discord is an evil. Allaah, The Exalted, says (what means): {No good is there in much of their private conversation, except for those who enjoin charity or that which is right or conciliation between people. And whoever does that seeking means to the approval of Allaah - then We are going to give him a great reward.} [Quran 4:114] Moreover, Abu Ad-Dardaa’ reported that the Prophet, sallallaahu ‘alayhi wa sallam, said: “Shall I inform you of what is more virtuous than the rank of fasting, prayer, and charity?” The people replied, “Yes.” The Prophet, sallallaahu ‘alayhi wa sallam, said: “Reconciling people; and beware of spoiling people’s relations for it is destructive - it strips you (of your religiosity).” [Ahmad and At-Tirmithi]
Allaah Knows best.