There are thousands upon thousands of laws in this country. Then broken down even further, adding each State law, city law, and county law, it is impossible for any one to know all of them. That's where Qualified Immunity come into play. Cops DO NOT get qualified immunity if they absolutely KNOW they are violating someone's clearly established rights. They are granted qualified immunity if they DIDN'T KNOW they were violating someone's clearly established rights, as long as they claim they were doing it in good faith and to the best of their knowledge of the law AT THE TIME. Because...how could they know? There are too many laws to know.
That is why cops become dumb on purpose. They know that it is 100% in their best interest to remain ignorant of any law. As long as they remain ignorant of laws, or at least pretend to, they can pretty much do whatever they want. That's why they have become nothing more than POLICY enforcers. They conduct themselves while on the job according to their department's policy, not law. All cops know this, and all cops conduct themselves this way.
And to go a bit further, a cop would STILL be granted qualified immunity for the same violation twice. How? Because both violations have to be 100% exactly the same. For example: a cop is being sued for falsely arresting someone for not showing an ID inside a Wal-Mart. He goes to court says that he didn't know it was against the law to arrest someone for not showing an ID inside a Wal-Mart, qualified immunity granted. You would think now he KNOWS it not against the law right? Wrong. A year later, same cop falsely arrests someone inside a hospital for not showing an ID. Now he claims, I didn't know it was against the law to arrest someone for not showing an ID inside a hospital. Qualified Immunity Granted!
This is why cops are dumb on purpose.