Genesis 9:6

English Standard Version

“Whoever sheds the blood of man, by man shall his blood be shed, for God made man in his own image.

I think I figured this verse out. The problem with telling it to people without the full context is the problem. Also the formatting of the passage is a Tell. The passage is right after God BTFO Humanity by flooding Earth. It's almost like God enters a Soliloquy and has a realization. Similar to when God learned a lesson with Cain killing Abel (not to openly favor one Child over another right to their face as this creates animosity between siblings). This is why I think God only punished Cain by driving him of his homeland, in fact, He protected Cain with a Mark where anyone who went against him would be cursed. So God let Cain live as some sort of reward for making God more Wise to His own creation (think of how you raise your own Child, or Pet).

So anyways, God BTFO Humanity, makes a covenant (agreement) with Noah that He won't flood the Earth anymore, and gives us the Rainbow as a reminder of that promise. Noah and his Bloodline were favored by God, and since Noah passed the test, God let Humanity live in a version 2.0. God gives Noah, and all generations after him (us), a lot more authority and freedom. Because God also said we are of his image, and 'evolve' together so to speak after also realizing Humanity is innately violent in their early years, as was God with the flood.

So, with all this in context now:

Whoever sheds the blood of man, by man shall his blood be shed, would lead the way into Man's Law. God trusted Noah and his future generations to be responsible for finding a way to punish Humanity for their sinful ways along with God (the covenant). This makes sense because in the same Chapter, God gave Noah and his future generations complete authority over Earth. You almost have to put yourself in God's (the Dungeon Master) position and imagine what kind of lessons you can learn from what you just did (growth of consciousness, Wisdom).