"Christendom has done away with Christianity without being quite aware of it."
-Soren Kierkegaard.
Christianity is harmed by the incessant attempts to yolk it with "us, them, we" or any personal pronoun other than "I".
It invariably leads not to closer brotherhood among believers, but to sectarianism, pride and judgment.
As an individual, a Christian is more likely than most to be humble, peaceful and understanding.
As a collective, or as a demographic, we can tend to be proud (of our Christianity), hostile (to anyone or thing perceived to be hostile to us as Christians) and judgmental (to anyone who does not hold our values).
As the individual Christian, we have a better sense of who we are in relation to world, and to God himself.
As "Christendom", we tend to find safety in numbers, establish insular subcultures, and hide behind our own theologians and teachers.
Christians lose something of the peculiar shame of the Cross when Christianity becomes accepted, respectable, a movement or even, God forbid, official.
We become quite at home in the world, and even begin to claim portions of it as our own. And become quite defensive and even combative when we feel that holy ground is being invaded.