Tim Keller writes, “These rules, I believe, will help us neither avoid polemics nor engage in them in a spiritually destructive way”:
1. Carson’s Rule: You don’t have to follow Matthew 18 before publishing polemics.
2. Murray’s Rule: You must take full responsibility for even unwitting misrepresentation of someone’s views.
3. Alexander’s Rule: Never attribute an opinion to your opponent that he himself does not own.
You can read the piece here for an explanation of each point.