Excellent point, Javier. But atheists and skeptics don't like it when we have to define for them just what a Christian is, as it tends to take away too much fire from their arguments against Christianity.So yes we need to define a Christian according to the Holy Word of God
I believe it was Justin Martyr (2nd century) who said, "He who does not follow the teachings of Christ, through he professes him with his lips, cannot be counted a Christian."
That's how this is answered to:
So how do you fit the massive displays of Christan violence and sadism through history? The Crusades, the purging of French Protestants, the glorious Inquisition, the Christian genocide of entire cultures in the Pacific Islands, the Christian collaboration with the Nazis, the "Just War" theory to allow Christians to participate in Vietnam, the use of churches as meeting places for the KKK... The list goes on and on.