Do people in a crowd start to behave in some sort of collective way, in which each person is influenced by those around them to such an extent that the crowd seems to have a collective will of its own and acts like a single large entity?
This belief forms the basis for the way that authority figures react to large crowds, with police cracking down indiscriminately, and often brutally, on everyone in the group for what may be the actions of a few isolated individuals, thinking that such force deters the crowd as a whole, rather than making the effort to identify and apprehend the few who may have caused the problem. We often see this with mass demonstrations that often start out peacefully. But when a few people start acting violently, the riot police will then attack the entire demonstration, starting with the people nearest to them, and the situation then spirals out of control.
This article suggests that this is misguided and treating crowds as a single entity leads to the wrong kind of responses, and risks making the whole situation worse. Furthermore, it enables provocateurs who have no sympathy for the causes behind the demonstration to disrupt it by deliberately provoking the authorities.