Is this a legitimate reason to be pulled over in NYC?

So I was driving home in the Bronx on the Bronx River Parkway (2 lanes at this point) in the left lane (people in the right lane were going like half the speed limit). At this point there is no one behind me and I am going the speed limit. Maybe 10 seconds later I look in my mirror again and there is a guy literally right on my bumper (closer than I get when I park and could barely see the hood of his car in my rear view mirror). I couldn't change lanes at this point because there were a few cars in the other lane. Eventually there was enough room for me to switch lanes, but before I could the car behind me swerved into the right land, cutting off the other driver. The car looked just like all the town car taxis and drove just as badly. He then sped up so he was right next to me then slowed to my speed and gave me the dirtiest of looks, so I flipped him off. That's when he turned his lights on and pulled me over and I realized for the first time that he was an undercover cop. As soon as he pulled me over he jumped out of his car and came right up to my window. Usually they run the licence plate or something first. This guy was on a power trip, starting screaming at me as soon as I rolled down my window, calling me and idiot among many other names. I told him I had no idea he was a cop and would have tried a little harder to get out of his way and obviously wouldn't have flipped him off (even though in my head I was thinking of punching this guy in the face for being such a douche bag). He finally asked my for my licence, so I searched my pants, but forgot it at home. The officer then started threatening me saying he would have the car towed and leave me stranded on the side of the highway (not the nicest of areas either). I then grabbed my Captain's PBA card, police union card (my uncle is a retired NYC police chief). After I explained who my uncle was, he snatched the card, told me it was my lucky day and started to walk off. As he was leaving, he said if I want the card back I could get my uncle to pick it up at the precinct and ask for him.

Was I doing anything illegal here at all that warranted being pulled over and being yelled at like that or was this guy just having a bad day and wanted to take it out on me? Is this something I should report to the precinct or should I just let it go?

FWIW we are both white, so race wasn't a factor here.