I'm curious how you would prove it? The biggest indictment of humanity to me is our destruction of the biosphere for future generations (and at the rate we're going, a few current generations as well).
I can enumerate the long list of policy that treats youth as a resource to extract from vs supporting and enabling their success. Is that what you had in mind for this?
No need to enumerate the list; I can imagine rather a lot of it, and it probably isn't limited to youth, but they're usually the least able to deal with those who would extract from them.
But I still think the largest indictment of humanity is our failure to care for our home. Buckminster Fuller gave us the idea of "Starship Earth"; that we are all the crew of a spaceship that winds through the galaxy and we must all cooperate to maintain it for those that come after. It seems almost certain now that we will not make it.
Is it that or something else?