Taboos around violence for political are one of the crucial building blocks for a functioning democracy. If those taboos are broken, even for a good cause, you set a precedence that violence works. And the next cause won’t be as good. One only has to look at the lessons of the Roman Revolution that started with the murder of Grachus, and ended with an Emperor who everyone acclaimed as they were so tired of the bloodshed.
We have a democracy. People have opportunities to vote. Police policy is decided largely at the local level, so individual votes are powerful. Imagine if even 10% of protesters voted in their local elections...
You can also see dirty tricks at local council meetings, where those in authority abuse the meeting’s rules of order to quickly shut down anyone speaking up about problems that those in authority don’t want addressed.