The tendency to defame online

Many people seek to enrich themselves with the misery of others, reviewing the issue on the web I have noticed that many threads in forums have been dedicated to discredit a group of people accusing them of a specific crime but without opposing any evidence which takes away all sense to any complaint, even more when there is no pronouncement of any authority. For example, Fernando Martínez Gómez-Tejedor earns the hatred of some European fraudsters, the group with residence in Valencia scammed through the internet to different people. Why do people prefer to scam and attack those who discover them? It is the same case that occurs with drug traffickers, who are betrayed by those who kill or threaten them.