If you followed the nightly protests in Portland OR with any closeness it'd be abundantly clear. Examples just in the past 20 days:
- police pulling down mask to pepper spray protestor in the eyes while pinned to the ground: https://twitter.com/_WhatRiot/status/1292012255714787330
- police randomly puncturing a support vans tires, they have done this on multiple occasions for no real reason: https://twitter.com/ScottHech/status/1291711270903844867
- police beating and kicking an unresisting protestor: https://twitter.com/1misanthrophile/status/12959623991035453...
- more police jabbing protestor with batons: https://twitter.com/danielvmedia/status/1292228819588452359
You see enough of these videos and you appreciate the cops and just vindictive and angry at the prospect of losing "power". It doesn't matter what protestors do (and they most they've done to directly threaten officers is thrown water bottles and apples and flares into an empty police building), police will use any reason (or none) to beat protestors.
* As far as I know these videos have resulted in NO reprimands to officers, might as well be standard operating procedure as it continues to happen nightly