Only in hindsight. The letters of Paul deal with a lot of divisions, as does the book of Acts. From there through the Gnostics, Arians, Iconoclastics, Orthodox, Protestants, etc. the history of the church has been to a considerable extent the history its divisions.
In fact, I would suggest that the only periods in which the Church has not been divided has been in periods when it conspired with the State to crush divisions by force. Which I don't consider a particularly Christian way to handle anything.
Well, I was thinking of just the division on this issue, which is a pretty big one, but I see your point. Of course, the other side would probably look at the same history and say that the “real” church never changed, they just had a never-ending series of heretics splitting off from them. If you take that perspective, then I guess you never have to worry much about Christian unity at all. Anytime there is an argument, you can just arbitrarily make a line, then say everyone on the other side of it is suddenly not a Christian anymore. Problem solved!