According to the definition of Mr. Le Bon, the members of a group of people normally behave differently as they were individually. Originally they could be very gentle and kind as individual, but after enrolled in a group, they will behave quite differently, much better or much worse.
As an individual, one may mostly care of himself and has his own target or purpose. such as win a game, and so on. If not, it can be a sight of difference. In this case, they may also do something, which they would never do as individuals.
Such as a lot of things we can see during the Culture Revolution of China, people never care of their own purpose, willingness, and all private things. They may even kill someone for the common reason of the group, because they believe that the group will be in charge of its duty but not their own. Or, they may hurt other people for their own reason without care of human being's rights.
For the people out of the group, they can never understand how people can do it. But, it is never a problem for the people in the group. That is the reason why I would compare "the Culture Revolution" of China with the WWII. Basically, they were happened due to the same reason. That was what I thought twenty years ago, much earlier before I heard about the Le bon's theory.
Unfortunately, this kind of things happens almost everyday, and for many of people.
This is only an initial idea and understanding. I need more time to think about it, and we can talk about it later in another time.