Not only that, Drake says the badge could let him kill Perry right then and there and get away with it.
Would that scene, not just the slur but the threat, have been written after George Floyd and the protests, the general awakening we've had of racial issues?
I'm not sure a black cop would get away with killing a white man in 1930s LA. Nor that cops are that well-paid in the Depression era, which Clara makes a big deal about, how he shouldn't oppose the LAPD establishment.
Certainly what Drake did and will do goes against his family's interests. Risking a job in this period would be highly unusual, no matter his sense of right and wrong.
So we see a black cop pursing justice against corrupt fellow police officers, kind of like the black cop in The Watchmen.
Della saved the day to rescue Emily as those cops were about to torture her. But would her catching them in the act be sufficient? Why wouldn't she be in danger? Those cops murder and torture, are corrupt to the hilt. Seems like she'd have to be streaming it live from a 2020 smart phone.
Some of the profanity in the dialogue seems out of place for the period. Not saying they didn't throw around the f-bomb but maybe it's more modern writers not bothering to try to render vulgar speech back then. The way Baggerly speaks seems more appropriate to the period. For instance, he blamed his youthful mistakes on "degenerate femininity" rather than calling the mother of his illegitimate son a whore or something else crude, the way Pete and other characters swear up a storm.
Of course Baggerly is suppose to be religious and consciously trying to avoid vulgar language.
Some other character referred to a female character as "gash" which may be something they might have said back then. But the overt crudeness isn't something that you associate with a period so long ago, only because even within our lifetime, casual swearing has increased over time.