Association and separation?
We face the social dimensions of this question on the bigger issues: when do we associate even if we might disagree? When do we separate because the issue of disagreement is too large.
How do we provide a framework of choosing?
In USA political life, there are two major parties and though one can be a member of the myriad of small parties, realistically, the only candidates getting elected come from the two major parties. Thus, one chooses a party based on which is most inline with one's views. No party matches us 100% so we live with this association but separate on particular issues.
The same would be true for aspects of the Christian community.
A simple example is the divide over infant vs. adult baptism. Some Christians feel very strongly on this point and would use that as one factor in selecting a church to be a part of. While others don't feel so strongly and it isn't a consideration in the choice of a church to associate with.
I am still working out frames to analyze the issue trying to balance ideals and practical realities.
Here is where I am at right now.....
On issues of broad social interest I think the net of association should be pretty broad. As an example, the battle against human traffic draws people from many points-of-view. On this issue, Christians, Jews, atheists, agnostics, secularists, feminists, liberals, and conservatives can all work together to fight this.
When it comes to the overall peace and prosperity of our city and nation, I would support the capable candidate regardless of their individual faith/non-faith. Thus, I'd rather vote for a capable atheist than a sincere but in-over-their-head Christian to be mayor of my town or whatever the post might be.
If the audience and concern is a bit more narrow then I would cast a narrower net. For example, a group of Christians are gathering together to have a conference on how to communicate the value of faith to youth. On this matter, my filter for association might be as broad as does the group and individuals in the group subscribe to the Nicene Creed or the Apostle's Creed. I might add that I would want participants to hold that the Scriptures are a trustworthy and authoritative guide to doctrine and practice. Beyond that we might have differences in points-of-view on other more specific areas of Christian faith and practice.
Where I am beginning to see some clouds in this analysis in that there are Christians who would probably affirm the Nicene/Apostle's Creed but demure on the high view of the Scriptures. Additionally, there are a number of "denominationally distinctive" issues. In some cases, disagreement on one issue might be discomforting to me personally but not a cause to break association. As an example, I think adult baptism makes the most Scriptural sense but I would not separate from a church that practices infant baptism over that issue. But what happens when there are a multitude of issues? At what point is there too many disagreements leading to a need for separation?