What is the ruling on a layman who debates an apostate and sinners during gatherings and among a group of people? I have heard that malicious allegations should be refuted if they are brought up in a congregation.

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.

The Salaf (our pious predecessors) have been quoted many times warning against socializing with followers of Bid‘ahs, to prevent a person’s heart being affected by their malicious allegations and then going astray.

However, anyone who is knowledgeable enough to ward off their malicious allegations should debate with them. Indeed it is sometimes obligatory to do so.

As for people who don’t have such knowledge, they are not permitted to  indulge in arguments about Sharee‘ah-based issues, for Allaah the Almighty Says (what means): {And do not pursue that of which you have no knowledge. Indeed, the hearing, the sight and the heart - about all those [one] will be questioned.}[Quran 17:36]

And Allaah Knows best.