“At some point, someone, somewhere is going to lash out at you. People will lose their temper and say, or more likely write, unkind words toward you in an attempt to draw attention away from their own inadequacies, shame, or embarrassment and try to cast all their emotional pain onto you.”
All you have to do is smile in these moments. Apologize for your own confusion at their response, and ask them for their help to resolve the matter. If your antagonist continues in his or her immature behavior, simply apologize again for your inability to understand what is being addressed or asked. Then, excuse yourself while still wishing your antagonist well in his or her endeavor to resolve this mysterious problem.