From what you posted it's really simple---there was no reason you had to get in front of the driver, or even alongside him. Once you saw his bad driving (cutting you off) from a safety standpoint you should've just let him go on and you stay behind him. Afterall if he's ahead of you he can't back-up & hit you. It sounds like the Officer was thinking along similar lines as I and perhaps he knew more about the incident than you (or I) know. Aside from that I don't know what you're asking. as to why he didn't tow the other guy's car---some agencies have a policy that limits conditions as to when a vehicle is towed no matter what the law says.