What is the ruling on revering people of innovation (Ahl al-Bid'ah)?

It is not permissible to rule that someone is an innovator (mubtadi') except after the conditions are met and impediments are removed. A Muslim should not publicize the matter of an innovator or boycott him; rather, he should advise him and clarify the truth to him. If he persists in his innovation, then he should not be honored and should be treated like a disobedient Muslim without publicizing his matter, unless he openly declares it and calls others to it. In that case, it is obligatory to make his matter clear to people so they may beware of his innovation. As for boycotting one who calls to innovation, it depends on the expected benefit. If the boycott deters him or reduces his innovation, then it is legislated; otherwise, it is not. Sheikh al-Islam Ibn Taymiyyah said: "And whoever is an innovator, openly displaying innovation, it is obligatory to denounce him. And among the legislated forms of denouncement is to boycott him until he repents. And among boycotting is the refusal of religious people to pray over him, so that those who imitate his path and call to it may be deterred. And Malik ibn Anas, Ahmad ibn Hanbal, and other imams have commanded something similar."