The spirit will be reflected in the preaching: It will be anti-Christ even though it proclaims Christ, which is really deceptive. The "anti" part will be revealed in a lack of submission to the doctrines or to the government of God.
This is very serious. God gave religion the responsibility to give moral, spiritual, and ethical guidance to man. If mankind does not realize the spirit behind the false preaching, he will naively reflect the evil spirit that is there.