What is the Ruling of Abandoning the People of Sins and Disbelief?

Regarding the Hijrah (abandonment) of the doer (of the deed), the doer must sometimes be abandoned. The people of Ilm (Islamic Knowledge) said: like a man who publicly commits a sin, who does not care about it (the sin), abandoning him is accepted if there is goodness and a benefit in abandoning him. And the goodness and benefit are that if he is abandoned, he would realize his worth and turn away from his disobedience. An example of this: a man known for cheating in selling and buying, so people abandon him. When they abandon him, he repents of this and steps back and regrets. A second person is one that deals in Ribaa (usury), so people abandon him and don't greet him or speak to him. So, if he knows this, he then becomes ashamed of himself and returns to his senses. A third person- and he is the worst of them - does not perform Salah (the Prayers). This is a Kafir (apostate), a disbeliever -and refuge is with Allah-. He must be abandoned; such that, his greetings are not returned neither he be greeted, and his invitations must not be honored. So, if he becomes aware of himself, and returns to Allah and Islam, it would benefit him. However, if the abandonment will neither be of a benefit nor do good, and is just for a sin not kufr, because if the abandonment is owing to kufr (disbelief), then the apostate disbeliever should be abandoned in all conditions, whether the abandonment is of benefit or not. But regarding an individual who commits a sin smaller than disbelief, if abandoning him will not do any good, then it is not permissible. (That’s) because the Prophet (ﷺ) said: “It is not permissible for a man to abandon his Mo'men (believer) brother for more than three days; they would meet and turn away from each other. And the better of them both is he who begins with the greetings of salam". The evidence for that is the story of Ka’b bin Maalik may Allah be pleased with him, Hilaal bin Umayyah and Muraarah bin Rabee’, who have lingered behind (instead of joining) in the Tabuk campaign. So, the Prophet ﷺ abandoned them and ordered Muslims to abandon them too. However, they enormously benefited from that. They benefited, they turned to Allah. The earth became narrow for them with its spaciousness, they felt distress, and they were certain that there is no refuge from Allah except to Him. So, they repented and Allah forgave them.