As specs has already stated, you won't be employed very long.
The first time you refuse to raid a home on a "no knock" raid, the first time you are told to "look the other way" in the face of open corruption, the first time you have to arrest somebody for no just reason, the first time you have to throw somebody in jail and ruin their life over a plant, that will be the make or break moment.
And you'll, if you're like most of us, shine it on, swallow your objections and follow policy, in order to keep drawing a paycheck and keep a roof over your head.
And every time that happens, it will get a little easier each time, a little easier to justify.
And in ten years, you'll be unable to distinguish yourself from what you used to hate.
Do yourself a favor, drive a cab, work an injection press, deliver pizza, continue in private security and save yourself the hassle.