Timothy Keller makes the point (The Reason for God) that every community is exclusive in some way. The right and the left of any issue form a community around certain beliefs and certain values that will exclude members of the community that rebel or don’t comply with them.
So to call Christianity an exclusive community separate from others is rather rich when a closer look at your own community will unearth a similar exclusivity. What should be considered in all communities is the value of how that community respects, love and care for other communities. What should also be carefully monitored is if the community condemns, violates, is aggressive toward and demonizes other communities not like theirs. No community is entirely inclusive of all people regardless of what their moral and belief structures are.
I would like to add that although Christianity is inclusive of all race, gender and class there is a value and belief structure that is expected of all its members. In saying that it is important to note that ‘grace’ is a fundamental doctrine of the Church and thus one often finds members who contravene the core set of values still being a part of its meetings and community life. It takes extraordinary circumstances for a mother to throw her child into the cold.