I hold that some things form our core beliefs (The Trinity, Christ as both man and God, His gift as complete salvation with our Faith in that as core, and our Works as a thank you to him for our pardon) are the Foundation of the unity of Christians. A lot of the other stuff is Tradition that is the beams, paint, drywall, and stained glass that makes the walls of our individual churches. As Screwtape might opine, one good way to make Christians ripe for folly is to get them to spend all their time arguing internally. With Muslims at the gates, and the civil government of many nations working at opening those gates in the name of diversity, it is well that we should stand together in the Faith, brother.
What C.S. Lewis called "mere Christianity" - the parts we can all agree upon.
And you're right, the barbarians are at the gates. I find I have far more in common with the orthodox (that is to say truly believing) Baptist, Evangelical, Russian/Greek Orthodox, or Jew than with the watered-down middle-of-the-road liberal denominations or with the frankly liberal screaming loons like the Episcopalians (of which I used to be one - but not liberal and rarely screaming).