|Sometimes even good people do not-so-good things.|
Before long the name-calling had taken on a life of it's own. People were saying the author had been the name-caller, and were taking the associated book off their to-be-read lists. I'm sure sales will be negatively affected.
On social media, least said, soonest mended, does not apply. If anyone representing you makes such a huge mistake, they must be called out, quickly and cleanly. In the above mentioned case, the author made no note of the agent's poor word choice, but simply continued her very public social media conversation. Much better would have been something like: "Please don't call X a B. She is a great book blogger and I appreciate her thoughtful reviews."
Perhaps the author was worried about offending her agent. Instead she offended hundreds of readers.
Like it or not, as authors we are public figures and must behave accordingly. I don't want to pass judgement on the agent, even the best of people have bad days and make mistakes, but what would you have done if you were the author and your agent made such a huge mistake?