Here's an interesting article from Roger Nicole: Polemic Theology: How to Deal with Those Who Differ from Us.
What Do I Owe to the Person Who Differs From Me?
What Can I Learn from Those Who Differ From Me?
How Can I Cope with Those Who Differ from Me?
Food for thought. Here's an interesting snippet:
How then do we desire to be treated? First, we want people to know what we are saying or meaning. If we are going to voice differences, therefore, we have an obligation to make a serious effort to understand the person with whom we differ. That person may have published books or articles. Then we should be acquainted with those writings. It is not appropriate for us to voice sharp differences if we have neglected to read what is available. The person with whom we differ should have evidence that we have read carefully what has been written and that we have attempted to understand its meaning. In the case of an oral exchange where we don't have any written words, we owe the person who differs from us the courtesy to listen carefully to what he or she says. Rather than preparing to pounce on that person the moment he or she stops talking, we should concentrate on apprehending precisely what his or her position is.
In this respect, Dr. Cornelius Van Til has given us a splendid example. As you may know, he expressed very strong objections to the theology of Karl Barth. This was so strong that Barth claimed that Van Til simply did not understand him. It has been my privilege to be at Dr. Van Til's office and to see with my own eyes the bulky tomes of Barth's, Kirchliche Dogmatik (incidentally, these volumes were the original German text, not an English translation). As I leafed through them I did not see one page that was not constellated with underlining, double-underlining, marginal annotations, exclamation points, and question marks galore. So here is someone who certainly did not say, "I know Karl Barth well; I understand his stance; I don't need to read any more of this; I can move on with what I have." Each of the volumes, including the most recent, gave evidence of very, very careful scrutiny. So when we take issue with somebody, we need to do the job that is necessary to know that person so that we are not voicing our criticism in the absence of knowledge but that we are proceeding from the vantage point of real acquaintance.