Is it permissible to pray behind imams who insult the Companions or claim the divinity of Ali (may Allah be pleased with him) or allege that the Qur'an has been distorted?

It is permissible to pray behind all imams, even if they are فاسقين (defiantly disobedient) or followers of a different madhhab (school of thought). However, praying behind the people of apostatizing innovations (Bid'ah Mukaffirah), such as those who seek help from the dead or insult the Companions, is not permissible under any circumstances. Praying behind someone whose innovation is not apostatizing is permissible, though seeking an imam other than him is better.