It's not a small adjustment in one's worldview, and it's normal and common for people who have benefitted from the false narrative to want to cling to it and reject contradictory evidence, as you pointed out.
You say that I want to reject contradictory evidence, but you never provide the contradictory evidence. Having a bunch of people convinced that the police are evil isn't contradictory evidence. Having people repeat your viewpoint isn't proof that the viewpoint is correct.
For an extraordinary claim you need extraordinary evidence. For something like your anti-police sentiment (which is funny because now all of the sudden nearly all police are evil, in all states, all counties, no matter the gender or race breakdown of the police, no matter what city/county/state/department laws and procedures are, all of the sudden police are all just evil? That's curious isn't it?) it isn't backed up by evidence. You can link to videos alleging "police brutality" but none of them that I've ever been linked to show such a thing. Of course mistakes are made, when there's millions of interactions between citizens and police every day, a one in a million or even one in a billion mistake still happens, humans aren't perfect. But for the claims you're making there should be extraordinary evidence, and there isn't any.
Now, somebody else in the world will read your comment and in some part incorporate it into their viewpoint, and repeat it elsewhere, just propagating the idea further.
Of course immunity leads to more bad behavior. How could it not?
You've never seen the Rodney King video?
Most of the people I know have been beaten or robbed at least once, or narrowly escaped being beaten or robbed. In almost all cases, the perpetrators were never caught. Are we the underclass?
The vast majority of cases of assault, robbery, and murder are not carried out by wealthy landowners or the police. If you're that concerned with people being beaten, robbed, and killed, your priorities should be different.
As for murders, most of them are from people you know, there is a vanishingly small chance that you are killed by someone that you do not know unless you yourself are a criminal.
But murders and beatings yes are an exception. Outside of times of war, where you again are likely to die or get seriously injured to protect the interests of the owner class.
Also, criminals are generally not prosecuted very often because it's not that important to the system that you get justice, really. With police, it's different, because it's not a question of not caring, but instead of actual accountability.
This is how you see someone getting beaten during an arrest and people are like "but this guy was once arrested for such and such". The assumption being, since they are "bad" people, that's the reason why bad things happen to them. And, therefore, that won't happen to "me". This requires one to ignore the fact that force wasn't called for.
In this particular thread you see that: "they must have been doing other things rather than just filming" – while we have seen multiple, documented, instances of people doing precisely nothing.
We also see "No True Scotsman": "What exactly is the definition of a journalist?". Which would be fine if we were just trying to understand the methodology, but not "these weren't actually journalists, therefore, they shouldn't count and everything is normal".