You were being preached to--the long standing practice of most Berlanti series. Contrary to the opinions of the ill-informed, the issues limply explored on the Supergirl episode in question have been addressed for decades. It is nothing new in media, and certainly not for black people in the real world who have labored, fought and bled on the streets, courts, law offices and police stations for generations. For anyone to even suggest this has been an ignored problem is--frankly--sheltered, or just continuing to push the opportunistic check-boxing BS of a Berlanti TV series.
As noted time and again, the life and plight of black Americans has never been the sociopolitical issue of choice/importance to Berlanti productions, so when an episode drops this 11th Hour, weak attempt to "do a black story" its end result is leaving a sour taste for those who know for Supergirl, this is coming out of nowhere (or pulled out of some other area).
Black Lightning's creators so effectively presented the landscape of black life in America--effortlessly weaving many of those complex issues into the everyday lives of its characters throughout its run. Of course, that was due to people who were the polar opposite of Berlanti and his usual cohorts, but what's worse is that two of the Supergirl episode's main writers were black, yet they were so out of touch, that they wrote like White Liberals trying to stand on a soapbox and seem relevant--shameful to be sure for Azie Tesfai and Holtham. You did not see that kind of lack of insight in the scripts for Black Lightning or The Falcon and the Winter Soldier.
Two black faces wrote the "original" story.
(Then 20 white people spent 6 months rewriting it.)