My grand-daughter is being "bullied" in pre-school. Other little girls mock her because she was wait-listed for a field trip to an ice cream emporium. And that's not all. It is routine.
People are evil. Unless an intervening force turns them around (partly or entirely) they will lie, cheat, and steal according to (a) the chances that they will get caught, and (b) the likely ramifications of being caught. Call it "original sin" if you must.
Note that there is nothing virtuous about not doing wrong when the likelihood of being caught is high or the ramifications dire.
Look at situations, cultures, and environments where parenting is lacking and the kids almost all and almost always turn out bad. This is the endemic problem with mother-led, single-parent households and the boys that come out of them. There is no sufficiently strong influence to turn them away from their natural hedonistic, selfish, vicious tendencies.
Look around the world at all the Russian emigres who are involved in major crime organizations of all kinds. Russia just came out of a situation where kids were taken from their parents and raised by a godless state FOR GENERATIONS. Is it any wonder that they are at the forefront of porn, countless scams, and international cyber-crime?
We should always be on the lookout for people and groups of people who are conspicuously virtuous: people who have high ethical and moral standards, who do well in school, who are accomplished but modest, people who give time and money to charitable causes, regardless of whether there is a tax deduction coming. And ask yourself WHY these folks are extraordinary.
Usually, there is a religious tradition in the family. It's not a coincidence.
Never forget that people of similar groups constantly search the crowd for authority figures who could pose the risk of being obstacles to their freedom or threats to their long established self-image. Because people lie themselves into confidence with a years long narrative of what makes them better than other group members, an encounter with a possible authority obstacle triggers one or more of several reactions.
For most of us, the common reaction is avoiding eye contact, looking at the ground with head bowed, or physically retreating out of the way. Members of the next sub-group deal with authority by engaging it in conversation or targeted diversion, in order to see how the perceived 'superior' being reacts. The last sub-group will divide into two opposite but behaviorally similar sections. Both raise their head, make themselves look tall as possible, and seek and maintain eye contact with the authority figure.
Where these last two sections diverge is, the first section will physically standoff with authority and use violence only to defend self or other weaker individuals, while the second will use force--if he assesses doing so is favorable and convenient--to take the property, freedom or life from those weaker.
However, all of the above changes when sub-groups of individuals gather and act as one mind and body. In this situation, even a large group of weak individuals can be persuaded--either by themselves or a single stronger individual among them--to act against their inherent nature, or the self written narrative of their lives.
In this human behavioral system we see a hierarchy take shape, a system of instinctual social interaction perpetuated and defined by image of self and ancient instinct. Layers of the hierarchy are fluid and often shift in very brief periods of the real time, evolving in tandem with whatever scenario or situation arises.
In understanding this primal hierarchy, we can then examine your statement: "humans are intrinsically evil".
Predators namesake in the animal kingdom is opportunistic and situational. Tigers do not always kill the prey animals in proximity to them; they only do so some of the time, depending upon benefit to self--which is usually to satisfy physical hunger. Human predatorial behaviors are no different on the surface but depart from the tiger in the human tendency to crave satisfaction for needs beyond physical nourishment or mating.
Human beings are also social animals. Keeping the group hierarchy dynamic described above in mind, mention must be made of how humans, in a group setting, want instinctually to please other group members; to belong to a group with well defined and superior characteristics, and satisfy a need to better the group at the expense of other individuals or groups. Add into this mix the almost subconscious drive to take the easiest or safest path to achieving the most beneficial result.
Finally, speaking to the hierarchy, we humans are, concerning our natural behaviors, constantly handheld through life for the purpose of keeping those behaviors in check, by perpetual limitation and modification of our will. This begins with two parents at birth--mother and father--continues with older or younger siblings, teachers, school principals, guidance counselors, child psychiatrists perhaps and then, after adulthood, workplace management, law enforcement and the courts. Of course, by late adolescence society expects us to have begun to master self-editing of our own behaviors.
To finally answer your statement with proper attention, evil is situational--foremost. But it is more complicated than that. The lifelong narrative of necessary lies we repeat to ourselves like mantras to forge our confidence is another prime factor. As is the success or lack thereof of our parental figures and sociocultural form of parenting by the society and tradition. In some cultures sexual assault of the weaker is permissible, for example.
In closing, I disagree that humans are by primacy predisposed to evil behaviors. Much like predation, evil acts depend on motivation, situation, possible reward, group think, real past personal history and the fictional id we create for ourselves and many, many more characteristics and randomized possibilities. I would agree however, that defense of self or family for real or perceived threat is where much violence can originate, followed closely by desire to please the group, and then--in the human mind--to satisfy one of countless needs or urges.
