The police are violent thugs everywhere, not just Republican cities and states.

It’s because they have almost complete immunity from being prosecuted for wrongdoing and also, well, they are incredibly well armed and often use their monopoly on violence to threaten blue politicians.

I grew up in a city where cops didn’t like their own chief of polcie because he wanted to drug test the force regularly after several got caught doing drugs on the job. The chiefs own force stalked him, harassed him, made violent threats against him and his family, until he was ran out of town. The police union sued him and said drug testing them violated their rights. The police union won in court. Those drug tests never happened.