I totaly agree, racing is stupid unless it's on a proper track. BUT racing undercover cop cars is not the problem. Its the idiots racing their mates (or cars they want to show off to) that are the problem and the D car will spot them racing and pull them up. I say good on them, they are just doing their job making the streets safer. But it's when they get all cocky and start trying to book you for everything they can... you just gotta hope they haven't had a bad day!
The undercover D car's have chosen to hide the fact they are cops, they will try to catch you out doing something stupid or a simple mistake. (Or just be lazy and wait near a stop sign for someone to drive though it without stoppig lol)
Undercover traffic police = Revenue raisers.
If they want to hide the fact they are cops then I say tough, tell everyone who they are. No sneaky business.