BBC replicated the experiment in 2002 and found that group dynamics and leadership were major factors in influencing the guard’s treatment toward prisoners, I.e. void of leadership - the guards were not motivated to participate in violence or abuse toward the prisoners. It’s covered in the doc and easily found online. That’s why I used that specific language when responding to what conclusions could still be derived from the study. However, given the obvious flaws in the design of the study - I’m in agreement that we should default to not knowing.