I intentionally did not read any comments beyond your original topic post. I don't want to get drawn into the trolling.
"They are not all bad." Of course this is true. Most Muslims are decent people that I would be happy to have as neighbors. They have a goofy religion, but so do Mormons, Baptists, and Catholics. This is America, and that shit is black-letter-law tolerated.
Of course not all cops are bad. I think a relatively small percentage are inherently evil. Like it or not, we need cops. Personally, I avoid them because they are not pleasant people, but they serve a valid purpose.
In both groups, the actions of a small percentage makes the whole group look bad.
Why are these two groups demonized? For the same reason any group is demonized: tribalism. That is human nature. The truly evil among us (the two political parties, and their lackies) exploit that human tendency for their own purposes.