[Asymo]

"He considered the lack of inner independance not a matter of IQ or innate cleverness, but rather a failure of character"

"For Bonhoeffer, this concept was deeply rooted in his theological beliefs"

I will make a Christian commentary on ignorance. Here by "ignorance" I refer to the deliberate act of not wanting to know (something close to the author's definition of stupidity, but within the Christian perspective the concept I explained is more commonly used).

Spiritually speaking, ignorance is a kind of arrogance. If reason reveals to us the order of reality as created by God, the ignorant person harms themselves and others, dragging them into darkness through their refusal to know. They act as if they have the right to harm others for the sake of their own desires; that is arrogance. As stated above, it is a failure of character.

[LelouBil]

Putting aside the theological part of your comment, I really like the definition of willfull ignorance as "a kind of arrogance"