I have not done any sort of research, but is my impression correct that the most egregious LEO abuse tends to come from the places with the most tyrannical .Gov and most restrictive 2A laws in place?
Here's one from Illinois.
Stay out of Illinois, folks.
There was a time when LEO behaved like Human Beings, because that's the way it was. Then they behaved because they never knew if the guy they were stopping might be armed. Then they behaved because they feared rebuke from the courts if they abused a Citizen. Now, LEO doesn't fear you, their bosses, or the courts. Look at the result.