Read about the 5 laws on Quartz.
Law 1: Always and inevitably everyone underestimates the number of stupid individuals in circulation.
Law 2: The probability that a certain person be stupid is independent of any other characteristic of that person.
Law 3. A stupid person is a person who causes losses to another person or to a group of persons while himself deriving no gain and even possibly incurring losses.
Law 4: Non-stupid people always underestimate the damaging power of stupid individuals. In particular non-stupid people constantly forget that at all times and places and under any circumstances to deal and/or associate with stupid people always turns out to be a costly mistake
Law 5: A stupid person is the most dangerous type of person.