People pull the "everyone knows" and "it's obvious" card all the time. It usually happens for two reasons 1) they don't actually understand the argument or subj

People pull the "everyone knows" and "it's obvious" card all the time. It usually happens for two reasons 1) they don't actually understand the argument or subject matter enough to explain what's going on or 2) they don't want to spend the time arguing on something they are certain is true