What the author is saying, I believe, is that if one 'believes' he should be sacrificing himself for such socialist claptrap as the 'common good' or 'higher cause' he has turned his back on God.
A Christian community, such as a mission or a monastery is different because these entities are wholly serving God. Through community they assist one another, but indeed the concentration is God and works pleasing to Him.
I am not sure that Jesus would be very comfortable with this narrow definition. Did Jesus not call us out in very specific terms to reach out to others. Indeed in the parable of the Good Samaritan Jesus clearly establishes that good works are not limited to people of faith. It seems to me that we do God's work anytime we respond to anyone that reaches out for help. Do you not think the whole tone of this thread is a little unChristian?