Seeing people as naturally aggressive and willing to harm others to promote their own interests leads to a zero-sum game mentality involving the assumption that in order for one person to do better, someone else must do worse. To go up one notch it is necessary that someone else must go that same degree downwards.
This narrow, individualistic take on how one progresses completely overlooks that acting in ways which elevate others is a powerful way to become valued and respected and thereby, elevating ourselves. Even among groups of primates, doing favors for others is a far more effective formula for success than just looking out for oneself.
The zero sum game mentality is a false dichotomy yet it is a delusion which many people fall under. We can see it throughout our culture, for example, in the upper echelons of corporate culture treachery, betrayal, and backstabbing is commonplace and barely covert; racists seem to believe that only by debasing the target of their scorn can they elevate themselves; and social media is replete with nasty, snarky, hostile commenters who all seem to believe that by putting someone down their status is enhanced.
When our sense of connection to those around us is sufficiently strong, we are disabused of the illusion that there can be any deep personal satisfaction when we harm others or treat them unfairly. People who feel the interconnectedness primary to being a healthy human can sense that any personal aggrandizement resulting from hurting others does not ultimately elevate them. Causing harm to others makes healthy people unhappy with themselves. And the degree they feel empathy for the party who was mistreated further diminishes any sense of elevation.
Even when the person doing the harm does not feel the slightest regret, whenever one person diminishes another for personal gain, it really always indicates a loss for both parties. In order to be impervious to those diminished around them, a person must have a significantly reduced sensitivity threshold from what it would naturally be in a person who is healthy, hence, in actuality both parties have been diminished. Indeed, depending on circumstances the person being harmed might be diminished only momentarily while the person who continually diminishes others is most likely far more deeply impaired.