A red herring is a dead fish which started to ripe and be smelly. Dog trainers trained the dogs to track under the distraction of a red herring scent of trail.
Here a red herring is an irrelevant topic which distracts us from the real problem.
Son: Dad, why did you go to see the movie "Star War" when you said I couldn't?
Dad: It was a really good move. I'll take you to see it the next week.