This just seems to suggest people are more likely to stop for in-group pedestrians or perceived authority figures.

I don't know why the title was changed. Is the white majority user base threatened by the idea that white people are overwhelmingly discriminatory against black people?

Perhaps the white majority userbase doesn't wish to be subject to racist generalizations.

Note that the article did not examine the race of the drivers, but you were quick to make your typical agenda driven and, frankly, rather racist judgement.

because hacker news has a rule about using the original title.

Wow. That's a rather impressively large generalization you've made there.