Many attorneys avoid being civil or diplomatic in their cases, as they want to zealously advocate for their client, but diplomacy can be an effective form of advocacy. While diplomacy is not a substitute for litigation skills, it does carry the following advantages:
Diplomacy Doesn’t Change The Merits: As discussed in Weighing Legal Arguments, cases are decided on their merits. A diplomatic approach does not weaken a strong case or strengthen a weak one.
Diplomacy Increases Credibility: As discussed in the Means Of Persuasion, credibility is one of the most important means of persuasion. Being diplomatic will increase an attorney’s credibility.
Finding Common Ground: It will be easier to find common ground if you take a diplomatic approach to your case. This is especially true in criminal cases, where the prosecution is not necessary looking for the longest sentence they can get, and are more likely to give deference to attorneys who are fair with them.
Reduces Risk & Effort: In general attorneys like to reduce the risk of litigation, and avoid doing unnecessary work. By discussing the issues in good faith an attorney can reduce the uncertainty and risk in a case by narrowing the issues (the less issues being litigated the less the risk). They can also decrease the work by avoiding unnecessary discovery, motions, and depositions by reducing the number of issues being litigated.
Pick Better Issues To Litigate: By discussing the case in good faith you probably have a better understanding of the issues in dispute, and are in a better position to Pick Your Battles.
CONCLUSION
Diplomacy is a long term strategy just as much as it is a short term strategy. Attorneys often run into each other after the case is over (this is especially true in criminal law). In the legal world it's better to not burn any bridges. You never know who you will need help from tomorrow.
This doesn't apply in every situation, and some attorneys need to be dealt with at arms length.