They aren't sick, they are just doing what they believe is "right".
To them, "The Law" trumps personal honor, and lying is required in some cases, so you may as well get on with it.
This is well known about LEO.. generally, they will lie their ass off to get admissions or confessions, and so on. For example, the whole "we'll go easier on you if you cooperate".
No they won't. They just say that to get you to spill the beans which, if you had said nothing, you wouldn't be sitting in prison.
So, if a person is not known to you personally as honorable in Real Life (as in, you've known them for some time) don't give any personal information to anyone.. ever.
The next time someone says "hey man, I have a domestic source..." just leave it alone. Why would they give that to you, a complete stranger?