After mentioning that those who deviate from the orders of Allāh are in categories Ibn Qudama al Maqdisi (d. 689 Hijra) mentioned:

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Section Two: The innovator, if he is one who calls toward innovation and the innovation is from those that will make him a disbeliever (bidʿah mukaffarah), then his matter is more severe than that of a Thimmi because he would neither agree to pay the Jizyah nor would he make an agreement to live as a Thimmi.

And if it is that his innovation does not make him a disbeliever, then the affair between himself and Allāh is less severe than the situation of the Kāfir without doubt. But in terms of detesting what he does (in terms of his innovation) then this is dealt with more severity than the Kāfir.

This is because the evil of the Kāfir does not extend (to the Muslims) as none of the Muslims would pay attention to his speech. And this is different than the innovator who calls toward his innovation because he thinks that what he is calling toward is the truth. He therefore becomes a reason for the misguidance of the creation and his evil extends (to the Muslims). Therefore openly displaying enmity toward him, boycotting him, being an enemy toward him, humiliating him, being harsh upon him because of his innovation and running the people away from him becomes more severe.

As for the innovator who is ignorant and unable to call (toward his innovation) and it is not feared that he would be followed then this affair is less harmful. And what takes precedence is that one should be kind toward him in giving advice since the hearts of the laymen change quickly. However, if advice does not benefit him and turning away from him would show hate for his innovation in itself, then it is preferable to turn away from him. And if he knows that this has no effect upon him because of his stubborn nature and firm belief in his heart (for the innovation) then turning away from him takes precedence, because if one does not show hatred for innovation it will spread between the creation and the evil of it will become common.

Source: Ibn Qudama Al Maqdisi, Minḥāj Al Qaasidīn pg. 123, Maktabah Al Islāmi Print