Christians, too, Must Obey God’s Messenger
[5:14] Also from those who said, “We are Christian,” we took their covenant. But they disregarded some of the commandments given to them. Consequently, we condemned them to animosity and hatred among themselves, until the Day of Resurrection. GOD will then inform them of everything they had done.
[2:62/5:69] Surely, those who believe, those who are Jewish, the Christians, and the converts; anyone who (1) believes in GOD, and (2) believes in the Last Day, and (3) leads a righteous life, will receive their recompense from their Lord. They have nothing to fear, nor will they grieve.
We are responsible for what we know. If a Christian finds the Quran they should find nothing objectionable in it, as they will recognize the truth like they recognize their own child.
[2:146] Those who received the scripture recognize the truth herein, as they recognize their own children. Yet, some of them conceal the truth, knowingly.
[6:20] Those to whom we have given the scripture recognize this as they recognize their own children. The ones who lose their souls are those who do not believe.
Christian Etymology:
Christian (n., adj.) Look up Christian at Dictionary.com 16c., forms replacing earlier Christen, from Old English cristen (noun and adjective), from a West Germanic borrowing of Church Latin christianus, from Ecclesiastical Greek christianos, from Christos (see Christ). First used in Antioch, according to Acts xi:25-26. Christian Science as the name of a religious sect is from 1863.
http://www.etymonline.com/index.php?term=Christian&allowed_in_frame=0
Christ Etymology:
title given to Jesus of Nazareth, Old English crist (by 830, perhaps 675), from Latin Christus, from Greek khristos “the anointed” (translation of Hebrew mashiah; see messiah), noun use of verbal adjective of khriein “to rub, anoint” (see chrism). The Latin term drove out Old English Hæland “healer, savior,” as the preferred descriptive term for Jesus.
http://www.etymonline.com/index.php?term=Christ&allowed_in_frame=0