There are many reasons why somebody might want to come across as scarier than they actually are. Perhaps they are trying to protect themselves or other people, or they feel like they have to do it to fit in. Far and away the most common motive, though, is that they get off on the idea of having power over others.
This is why those who put on the tough guy act are above all annoying; many conflicts are much better solved when you try to meet others on their level, rather than scrambling to rise above them. However, you'd have a hard time telling that to the many individuals out there who are bonded like glue to their superiority complexes. If we all have to endure these kinds of people at some point in our lives, we should at least have a free pass to laugh at them. A list like this allows for exactly that.