Your world is a perfect syllogism, isn’t it? These are the people who we define as trustworthy, therefore we should always trust them, and damn the evidence to the contrary.
If police had not, in hundreds of ways and over thousands of incidents, shown themselves to be prone to lying, violence, and the violation of citizens’ rights, you might have a point.
The problem is that a staggering amount of evidence demonstrates quite clearly that, even though we should be able to trust the word of the police, we often can’t, because they seem, as a group, to be no more honest and trustworthy and reliable than the criminals that they are supposed to protect us from.
My stepfather is a retired police officer. My mother spent the last 12 years of her working life as a civilian worker in a number of large police stations. We had cops around our place a lot, and they all seemed like great people who took their jobs seriously. But despite my belief that being a police officer is an admirable and important job, and despite my predisposition, based on my own personal experience, to trust and respect the job, i no longer have confidence that a randomly-selected police officer is more trustworthy or believable in a he-said-she-said situation than any other random stranger.
I didn’t come to this belief because i’m a cop-hater. I came to it because a mounting pile of evidence suggests that too many cops are bullies and assholes and liars who take the job precisely because it allows them to get away with being bullies and assholes and liars.
One of my best students at the university where i teach told me the other day that, when she graduates, she’s applying to join the San Diego Police Department. I told her that was great, and i really meant it, because i think that the SDPD will benefit from the addition of a thoughtful, intelligent, socially-aware person who really wants to do some good in the world.
What we need is police forces who actively look for this sort of person, rather than take any power-hungry bully who wants to strap on a badge and gun. And we also need our police hierarchies to make clear to the good cops that it is acceptable—nay, that it is essential—for them to help root out the bad ones.