Scattered among the wheat in Christian churches are the tares sown by the devil (Matthew 13:25-36). Like Judas, they may look like the wheat. They preach, they teach, they hold office in the church.
They speak pious words and often may use the right terminology. But since they have been planted in the church by the devil, they're there to do his work to destroy the church, to stumble the true believers, to hurt them, to hinder their love for Jesus Christ and cause them confusion.