Can I really receive a citation for flashing my lights at another driver?

[Dave J]

I started to flash my lights at another driver who is a bad driver. I kept flashing my headlights at him for about 5 miles. A Utah Highway Patrol trooper approaching from the other way made a U-turn and started to approach me and this driver and turned on his police lights. Me and the other driver pulled over and I thought for sure the other driver finally was caught by the police for doing something wrong. To my surprise, the trooper walked over to the other driver and signaled for him to proceed back onto the road. He then asked me to turn off my engine. To make a long story short, the trooper said that it is illegal for me to flash my headlights at another car and will just warn me this time. I asked him exactly what is illegal about flashing my lights at another car and he told me that it is considered harassment. I tried to look it up in the Utah Driver Handbook and it doesn't mention this. The only things that are illegal regarding lights according the the Utah Drivers Handbook is using high beams within 500 feet of another car, equipping your car with blue and red lights that can be seen from the front, using strobe lights, and using spotlights. Is this trooper right or is he trying to get me to stop flashing my lights at another car by quoting a law that doesn't exist. Where does it say in the drivers handbook that this is illegal?