Seems that Justice can only happen when the God of Justice arrives and enforces it. Man is limited and can only do some, but not enough.

I don't think its stating 'not to know the truth' of things going on - that the enemy of fallen d'vils / demons are running the world's social realm system - rather that the depths of their insanity and evil is so extensive and extreme that humans can't conceive of it - too sickening, ugly, and perverse.
Those humans who are enticed by the vile evil lose their souls to it.
Jesus told Nicodemous “If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things?” John 3:12
He could've added 'worldly things' meaning the social arena.
Knowing there's evil is one thing, knowing the extent and details isn't necessary and harmful.
We pray: "deliver us from evil"
'don't even seek it out or entertain it'