I don't know what kind of proof or sources would satisfy you; I concur with the earlier poster that claims that this kind of thing should be considered a 'water is wet' statement, but if I thought that police conducted their affairs 'by the book', i'd have some questions and misgivings about the disproportionately large sums of money that come out of city coffers to pay for settling police misconduct cases[0].

or i'd check out Justice Robert's thoughts on fourth amendment violations with regards to violent police actions[1].

Apparently getting shot can be considered a seizure; plenty of people every day shot in the midst of unwarranted and illegal police actions, by police officers who often fail to convince the courts that their actions could ever be considered reasonable.

I'm not going to bother linking data about 'Police Brutality United States 2020' or 'Police Misconduct United States 2020' -- the datasets are numerous , feel free to google those phrases. I feel as if I were to link one you'd just judge whichever I chose

For every law enforcement officer, who you may anecdotally know personally, that does things 'The Right Way', there is an un-told number of LEOs that fail to share the same altruistic and noble priorities that your friends might.

[0]: https://fivethirtyeight.com/features/police-misconduct-costs...

[1]: https://news.bloomberglaw.com/us-law-week/woman-shot-by-poli...

Something I hold as a truism about humans is that most individuals are good and honourable, but collate these good people into a large group and the result is generally terrible and untrustworthy. I don't see any reason why that wouldn't also apply to people in law enforcement.