Actually they can and do defect people for whatever they like. Steveo got defected for having too many km's on the clock and something, I think it was the airbox, was "too shiny". I kid you not.
Now obviously the defect doesn't stand up to an engineers scrutiny, or a court's for that matter, but this doesn't stop them from issuing it in the first place and wasting your time and money to get it cleared.
The problem really is there are too many laws for the coppers to fully understand, and it's not just them, there's too many for anyone.
It's my opinion that most kids start off with a good opinion of the law but sometime from their late teens to early twenties they have at least one, if not a number of bad experiences with coppers. When I was younger I was pulled over and harassed regularly. I was usually polite and nice to them but let's be honest, if you are just cruising along, minding your own business, doing nothing illegal and you get pulled over and questioned like a criminal, threatened if you ask a question, no matter how polite, you are not going to think highly of anyone in that uniform.