So which traffic law would you honestly cite your wife/mother/pastor for then? Unless you're willing to write them a traffic ticket then they get a free pass as well. Keep in mind that my understanding is that we're discussing traffic infractions, not actions that fall under the misdemeanor category such as OWI, reckless driving, etc.
I don't know. I wouldn't make a good cop, I know that about myself. Let's say though, that I use my discretion in this way: I will let people off from speeding if they are polite, if they have a good excuse, if they don't have any other infractions, and if they are less than X% above the limit.
I hope I would write that ticket if one of those people didn't fit my criteria.
Again, though, this is much different than never ticketing cops for several reasons. One, I'm very unlikely to constantly stop members of my family. If I were a cop in a small town and related to half the people there and I always let my family go, that would be corruption.
These are two different things.