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 is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If the innovators are the type whose innovation take them out of the fold of Islam, like believing that the Quran was forged, or saying that the companions are non-Muslims, or saying that a given Imaam or any specific person controls the world, then such innovators should be treated like non-Muslims, one should not say Salaam to them, exactly as one is not permitted to say Salaam to non-Muslims, like Jews and others. Furthermore, one should not say Salaam to an innovator who propagate and calls to his innovation, as we are ordered to cut relations with the disobedient people, as this cutting of relationship is for the purpose of bringing a benefit. Imaam Ahmad said: 'It is an obligation to cut relations with the people who went out of the fold of Islam because of their innovation, or became dissolute because of it, or call to an innovation that leads people astray or makes them dissolute.'
However, if a person's innovation does not take him out of the fold of Islam and he is not a caller to his innovation or does not propagate it, then it permissible to say Salaam to him like any other Muslim with the expression 'As-Salaamu Alaykum'.
However, a group of scholars are of the view that it is desirable in general not to greet the innovators with 'As-Salamu Alaykum' whether or not they call to their innovation. Imaam Ahmad gave this ruling in some of his Fataawa.
Ibn Muflih said: 'It appears that there is no difference between an innovator who calls to his innovation and other dissolute innovators.'
Imaam An-Nawawi when speaking about an innovator and a dissolute person who openly shows his dissoluteness, said: 'It is not desirable to say Salaam to him, rather it is desirable not to say Salaam to him, and this is the view of Ibn 'Amr and Al-Bukhari.'
Allaah knows best.