My understanding is that this experiment has been discredited and I am quite convinced that its conclusions were manufactured. This would lead me to the proposition that human evil is largely predicated on social structures so that individuals tend to be led into evil, cf "lead us not into temptation". In my thinking this experiment only reinforces that deliberate evil is a distortion of the human psyche rather than a switch that only needs turning on.
However, I'm pleased that your assessments don't generally rely on the findings of this experiment and I every much like the way you've led us through the thought process. Another thought is that the Christian notion of evil puts far too much emphasis on individual morality. This not only presents a general feeling of guilt (original sin) which only makes things worse, it also degrades the idea of corporate guilt which is probably why Christian institutions have got away with so much evil through the ages.
What we now see on our screens only reinforces my belief that humans are naturally inclined towards good because the most evil and disturbing incidents presented to us are excused and promoted by the few who own all the wealth and control all the power.