[bluecalm]

>>That is, maybe you find that you can make a very good decision based solely on age and number of friends who committed crimes, and don't take race into account at all -- but then this algorithm ends up yielding "yes" to most white people and "no" to most black people, you haven't solved anything.

It would actually solve the problem. It's ok if I give more "no's" to black people as long as black people are more dangerous in general. It's only not ok if I punish a specific non-dangerous black person just because they are black.

That's what fairness is: you get what you deserve because of your decisions and wrongdoing not because how you look or where you were born. That some groups end up with more convictions is expected and doesn't contradict fairness principle.