User blog comment:Suparockr/List of Plotholes throughout the series/@comment-5020188-20120719202844/@comment-1221773-20120719203428

That's not a plot hole. The Council is just in denial. They're politicians and their first reaction is to downplay any threat to the galaxy to prevent panic and instability. They don't want to believe that the Reapers are real because it takes them out of their comfort zone.