If there is no other place to pray Eid prayer other than behind a defiant Imam (the Imam is involved in soothsaying), can one do it?

Soothsaying involves practices of shirk and kufr that take away a person from the fold of Islam. Firstly, the Imam should be advised that these acts are haraam, presuming that he is engaging in them based on ignorance. If he persists in these acts after being advised, then it would not be correct to pray behind him.