Agreed. What they inherit from koans appears to be merely the violence that the koans take for granted.
My favorite example of this is the story of Gutei's Finger:
It is said that Master Gutei would always raise a finger wisely when
teaching about Zen. Now in his monastery there were young boys studying
to be Zen masters themselves, and one boy, when he was asked questions
by his teachers, began also to raise his finger when answering Zen
questions. The teachers told Gutei about this and Gutei summoned him to
a rare audience with the master! Gutei asked him a simple question which
the boy could answer confidently, and the boy raised his finger as he
responded.
Gutei immediately grabbed the finger and in one motion cut it off with a
concealed knife. The boy screamed and ran to the far side of the room.
Gutei called him to stop and return, and the boy recovered his composure
and plodded back in front of the master. Gutei raised his own finger
before the boy, and in that moment the boy was enlightened.
Indeed, on his deathbed Gutei's last words were: "My teacher Tenryu
taught me the Zen in my finger, and though I used it my whole life, I
couldn't use it up."
I think the first thing anybody notices about this story is just the violence. When I told it to my brother he asked, "the lesson is, do not f--k with the Master?" But there is a deep set of Zen ideas -- lifting fingers which you do not have, and not getting attached to idiosyncrasy. Perhaps the boy even thought, "I should cut off the Master's finger," as he attained enlightenment.
Violent koans aren't particularly common, they just stand out. However, they do reflect a fundamentally destructive aspect of spiritual practice, namely, that it undermines the conditioning behind cherished identities. The point of the story is that the boy was chasing after validation as a Zen master and had adopted the finger-raising ritual as a part of his identity as a competent Zen practitioner. When Gutei cut it off, he was removing a support for a cherished identity, and this was the basis for the boy's identity at that moment.
I think, like almost everything, the Koans are a reflection on the society and the way of thinking at the time of writing. In what is now peacefuller times people would be aghast that someone would do that. I dug around through a few, and a lot of them feel a bit too meta for me, though I did find the Hello World Koan to be an interesting discussion on our flippancy with code: http://thecodelesscode.com/case/14
