I firmly believe that most Chicago police officers are good people and are just trying to do the best job they can. This is from my personal experiences, especially around Wrigley Field where I've time and time again seen them de-escalate issues with drunken idiots.
I also firmly believe that there are some bad cops who do terrible things. This is also from my personal experience of receiving hundreds of phone calls from different people who report being harassed, beaten or otherwise abused by the police for no good reason.
Some of these callers are of course not telling the truth, but the great majority are. Imagine you are sitting in your house and the cops break down the door, point a gun at you and then ransack your house, leaving it in tatters, only to discover 45 minutes later that they were in the wrong house. That happens. Imagine you are walking home, minding your own business and not only do the cops stop you because "someone who looks like you" was reported to have committed a crime in the area, but when you ask them why they stopped you, you get punched in the face. That happens too.
Imagine you get rightfully pulled over or arrested for smoking a joint and getting the crap kicked out of you. It happens. Or having a gun drawn on you in this minor situation and being told that your brains will get blown out if you move.
All of these things happen all of the time. These are the reasons NFL players are taking a knee as well as of course the unjustified killings of unarmed black men and other aspects of racial inequality. Unfortunately, most calls I get that are like these situations go nowhere.
The only way to win a case like these and get a good result, especially if you don't end up with a big physical injury (e.g. the cop punches you and shatters your eye socket and you go blind) is to have someone get everything on video. These cases are very expensive ($50,000 or so in costs) so if you don't have large damages it's a big risk for a lawyer to take on a he said-he said case. But if it's on video that you have your hands at your side and a police officer jumped on you or video shows them kicking you while you are handcuffed, it makes a big difference.
It may be unfair, but the video not only helps clear away the uncertainty, but it adds a shock value that causes Aldermen for the City of Chicago to be willing to settle cases. It's no different than the Ray Rice NFL video. When you heard he punched his girlfriend it sounded bad, but when you saw it, it ended his career.
Of course it's not very easy to videotape someone that is hitting you or has a gun pointed at you. So often you count on your friends that are with you or Good Samaritans to take video for you. It's why I personally think that every officer should be required to keep body cams on the whole shift and that such video should be live streamed to anyone who wants to watch it. It will protect the public and protect the officers, especially the good ones who get wrongly tarnished by the acts of the bad ones.