It's not so implausible, actually.
"In 2019, 88% of the time L.A. County sheriff’s officers spent on stops was for officer-initiated stops rather than in response to calls. The overwhelming majority of that time – 79% – was spent on traffic violations. By contrast, just 11% of those hours was spent on stops based on reasonable suspicion of a crime." [1]
If police are mostly spending their time doing discretionary traffic stops, and using a criteria for those stops that ignores most white drivers, then "Pretty much all they do is harass and commit violence towards minorities" is accurate, at least in terms of time spent.
It could be simultaneously true that LA County sheriffs spend somewhere between 0.1% and 5% of their time playing a crucial role in society. It would be great to know whether this was true!
1. https://www.reuters.com/legal/government/police-are-not-prim...