Final answer:
Sub-groups can become dangerous due to their capacity to grow, increase cohesion around controversial goals, and foster exclusion or violence. Large groups with divisive ideologies are more likely to drive hate crimes and marginalize others. Group narratives manipulated for political aim also contribute to these dangers.
Step-by-step explanation:
Sub-groups can become dangerous when they grow in size, as they can exert more pressure to achieve their goals, which may include controversial beliefs or exclusionary practices. The larger a group, the more potential it has to garner attention, but also the increased risk for division and lack of cohesion. Hate crimes, for example, are often linked to in-group versus out-group dynamics. Those excluded or tormented due to group dynamics often face significant adversity and violence. Furthermore, with the increase in group size, there is a higher chance for individuals to 'free ride', exploit the commons, and engage in factional behavior that threatens the broader community.
Political and group narratives are frequently manipulated to create opposition and harm competitors, perpetuating intolerance and oppressive ideologies. Such conditions pave the way for confrontations and violence. When paired with the human tendency to be suspicious of strangers and factious leadership, small sub-groups with harmful ideologies may expand into larger, more pervasive movements with the power to enact widespread harm. Additionally, the separation of groups along geographical lines can simplify the marginalization of certain populations, making it easier for groups in power to isolate and disadvantage others.