Fighting the Good Fight of Faith

Sometimes I hear Christians say, that different Christian denominations need to lay aside our differences and unite for the cause of Christ.
I both agree and disagree with that statement.

I agree that we should all get along and work together to help our cities come to know Jesus Christ.
Tonight I went to a prayer meeting with some other pastors from Eger, and I will have another one later this week. Our church often takes part and sometimes organizes events with brothers and sisters from different Christian denominations, and I am glad that in our church I see absolutely no hard feelings towards other groups or any elitist attitudes. Another good thing, is that our church is in a good relationship with the whole spectrum of different churches in our area.

However, I disagree that we need to lay aside our differences completely and "unite."
We don't need to unite, since we are already united in Christ - we are already part of the same family - we cannot become any more united than we already are, by doing something together. Paul said "[be] diligent to preserve the unity of the Spirit in the bond of peace." (Eph 4:3) In other words, we don't need to "create" unity, we just need to "preserve" it - not tear it apart or stir up dissension.
Some would say, "Well, yes, but that is just passive unity - we need to also have active unity." The reason "active unity" doesn't always work well, is because many times when someone organizes one of these interdenominational "let's all do something together" events, they don't really want to work together - they just want other people to do their thing, and the other people, understandably, don't like that.
And I don't think that unity means completely laying aside our differences either. I think that, for the most part, we should celebrate our differences. There are lots of different types of people, and there are different styles of worship, which some relate to better than others. Different Christian groups reach different types of people because of their different styles.

Here's an example of two groups of Christians who are not celebrating their differences.
Greek Orthodox and Armenian Orthodox monks were preparing for a ceremony in the Church of the Holy Sepulcher in Jerusalem this past Sunday, when a disagreement led to a full-on brawl, which had to be broken up by the police.
Here's a video, and here's the article about what happened.
I don't think this is what Paul meant when he said "fight the good fight of faith," and I hope that things never get to this between any of the churches in Eger!