I wouldn't say that humans are "Evil" per se... but they are "Children" if you understand my meaning.
Humans have Instincts that are left over from when we actually NEEDED them.
Territoriality, Reproduction (The behaviors involved), etc...
In "Society" or "Civilization" we must work to "Domesticate" ourselves, so that we may live together for the mutual benefit of all.
The problem is that humans tend to revert to their old instincts fairly quickly when they have license to do so.
Like in the case of those in power.
People in power have their "Territoriality" instincts take over, (Because they are less constrained by the dictates of society, and the necessity of
society) and thus, they inevitably go mad with power lust.
This manifests in Western society as corporations lobbying representatives to pass laws that are benefit to THEMSELVES, at the expense of the rest of
the populous.
On this subject, I am going to have to refer to Frank Herbert:
All governments suffer a recurring problem: Power attracts pathological personalities. It is not that power corrupts but that it is magnetic to
the corruptible. Such people have a tendency to become drunk on violence, a condition to which they are quickly addicted.
-Missionaria Protectiva,
Text QIV (decto)
-Frank Herbert, Chapterhouse Dune
-Edrick