system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it that in groups humans are so naturally passive(Bystander effect), yet individually humans are usually very aggressive?(If you see a homeless man you want to give him a dollar)
gpt
In the instance that something terrible is happening in public (say, an assault), individuals tend to diffuse their personal responsibility for the situation to those around them; the bigger the crowd, the more culpability is dispersed. That being said, groups are constructs which can and often do facilitate violence far beyond what individuals are naturally inclined to engage in.

The same abstraction that allows individuals to shirk responsibility for intervening in the bystander effect also facilitates violence in groups. By identifying with and contributing to the collective, individuals can ascribe culpability to the institution and its members; ergo, the individual achieves a degree of anonymity (Grossman, 1996). This makes it much easier to rationalize ones actions and absolve one's self of guilt.

Moreover, within groups individuals feel compelled to support their comrades, particularly when their failure to do so would identify them as the weak link. This is a cornerstone of military strategy; artillery units, for example, are much more likely to fire at the enemy in earnest because the individuals must work together (Grossman, 1996). Knowing that others depend on you and are watching is often enough to override our natural (and strong) disposition to avoid killing.

Additionally, when we do experience situations that we don't understand and feel as if our lives have spun out of control, groups provide an opportunity to regain potency, order, and meaning. They are much more manageable, provide a sense of identity, and serve as a catalyst through which an individual member can exert power. Naturally, groupthink begins to creep up and overcome reason, posing a threat to peaceful resolutions to conflict (Fuji, 2009).

TL;DR: Groups  can act as a catalyst for violence by natural tendency to construct a framework which focuses, galvanizes and reifies aggression by way of cyclical reinforcement.