It is the present fashion to call Zeal by the name of intolerance, and to account intolerance the chief of sins; that is, any earnestness for one opinion above another concerning God's nature, will, and dealings with man,—or, in other words, any earnestness for the Faith once delivered to the Saints, any earnestness for Revelation as such. Surely, in this sense, the Apostles were the most intolerant of men: what is it but intolerance in this sense of the word to declare, that "he that hath the Son hath life, and he that hath not the Son of God hath not life;" that "they that obey not the Gospel of our Lord Jesus Christ, shall be punished with everlasting destruction from the presence of the Lord;" that "neither fornicators, nor idolaters, nor adulterers, nor covetous, nor revilers, nor extortioners, shall inherit the kingdom of God;" that we must not even "eat" with a brother who is one of such; that we may not "receive into our houses," or "bid God speed" to any one who comes to us without the "doctrine of Christ"?
--Blessed John Henry Newman, "Christian Zeal",
Parochial and Plain Sermons, Volume 2.