Group think
In social psychology, group think is the process by which a group of people collectively create what can perhaps be thought of as a mind of their own. Together, they synthesize a consensual reality which then often becomes resistant to change. Mind guards are members of the group which protect its members from thoughts counter to the group's consensus.
A key part of the process is belittlement and ostracism of anyone voicing unorthodox opinions.
One of the drawbacks of groupthink is that it can allow the group to take more radical positions than any of the individuals might have wanted. Then situations such as the French Revolution occur.