The Fundamentals of Copyediting
The Angry Author
Sometimes you will encounter an author who, despite best efforts, intractably insists on something outrageous or is just a nasty, hostile person. It happens. The first thing that you should do is keep yourself calm and keep from escalating the situation. State that you understand that the other person is upset and that you will handle the situation to the best of your ability. Let them know how feasible it will be to change the article: if the paper is still in its editing stage or in revisions, this is an easy matter; if the issue has been postscripted, a Corrigendum may be necessary depending on the problem. You may have to tell the author that you will contact them with more information at a later time after you do some detective work to find out why something was changed from the original. When discussing the problem, do not focus on (or even really discuss) whose "fault" it was. Instead, after acknowledging the author's feelings on the matter, give a general apology because you recognize that they are unhappy, and shift the author's attention to the fact that the matter can be resolved.
Whenever possible, remember that e-mail is your friend! You will always have an easily pastable, dated record of the matter and the exact words of you and your correspondent. It can be printed and put in the folder as a warning to others or given to your Journal Supervisor or Editorial Manager. If your initial conversation with the author was by phone, tell them that your next communication will by via e-mail, and keep all subsequent contacts that way (even if they respond by phone again). Make certain that the author understand that it is to keep things more clear for everyone concerned.
After any mentally trying contact, be sure to talk to your Journal Supervisor and/or Editorial Manager. They should be informed of such matters because 1) they don't want you to be upset, 2) may want to contact the author themselves or have a prior understanding with the author, and 3) have concerns regarding the production of the article. Why keep dealing with a jerk to yourself? You don't have to go it alone. Share the joy and let everyone know! After all, many times the same author will write papers for us again, and your experience allows things to be easier for everyone in the future.