It's rude to call someone out on their rare mistakes.
James is under a lot of stress because of tight deadlines when a coworker accidentally deletes a day's worth of work.
James wants to vent his frustration.
James takes a quick break and calls his wife from outside the building to complain about the coworker.
James yells at his coworker, calling him incompetent and a burden.
James feels calmer after talking to his wife and can concentrate on recovering the files.
James' coworker holds a grudge and ignores James' requests whenever he can.