A reporter is running an exclusive series of stories about serial killings. He's getting exclusive interviews with an active serial killer and even goes on one of the killings with the serial killer so as to accurately report just what goes on.
He refuses to help the police locate this guy. He's "protecting his source", so I guess it's okay.
Extreme example, but just goes to show that it is not always okay to protect your source. Now if you accept that (that it is not always okay to protect a source), you're redeemable. Now we just need to agree where the line is drawn.