bad traffic stop?

I was recently pulled over by a town patrolman. when I asked what the violation was, he responded “I’m doing commercial vehicle enforcement tonight.” I asked again and he asked “what is the gross weight of the vehicle?” I answered him and he asked if I had road flares on board, wheel chock blocks and reflective triangles. I didnt have them (apparently required in mass for vehicle my weight. stupid democrats) he then wrote a ticket which also included no owner lettering. now according to ma law, he was right ,but he didnt stop me for that. he never really told me of the original violation that he pulled me over for. so iguess my question is “can a patrol officer in ma do commercial vehicle enforcement on a random civilian with no violation prompting the stop?” I always thought that the only authority that could do that is a DOT officer or an officer from either the RMV or the state police Truck Team. Sure, he could have seen there was no lettering on the truck, but he never said anything about that until after he ran my plates and came back to the truck. Another question I guess was the officer going outside of HIS rights by pulling me over with no violation and were my rights infringed upon? I’m going to pay the ticket after all he WAS right about the laws or should I fight it?