I don't want to focus on just this case, or any one case, because crucial details are inevitably obscure, and any time you start digging into them, someone's emotions inevitably get stirred up, which tends to make any available information suspect.
I think the sad state of the economy has a lot to do with it. People who want a good job, but don't have one, are resentful of people who do. And people who do have good jobs are deathly afraid of losing them. If you are a police officer with a family to support, you are going to be loathe to give up your job with it's salary and benefits, so much so, that you might be inclined to ignore any internal problems your gang might have.
On the other side, we have neighborhood communities who have developed their own culture. I don't know whether it is minorities, poor people, or maybe it's just people who have warm hearts and have not learned how to be cold hearted capitalists, but they care more about their gang than any nit-picky little laws 'the man' might be trying to enforce.
The War-On-Drugs is part of the problem. Because the profit margins are so high, it provides people with a way to make a living. Because it's illegal, it is a constant source of friction between the police and those communities who earn their living from it.