Was I wrong for giving the car in front of me "the brights" or was he wrong for reacting aggressively?

I live in the NY metro area. Today I was driving to my parents’ house, and to get there, I take a two lane highway where drivers typically drive between 65 and 80 (left lane). Left lane is traditionally the “passing lane.”

Around here, if you are not driving fast in the left lane, you risk getting cut off from the right. I will drive between 70 and 75 in the left lane. People will drive faster and when I see them, I will get in the right lane. When someone tailgates me or flashes me the brights I will get out of the way.

Today, I came up to a car in the left lane that was going probably 50 or 55. I flashed my brights (it was daytime). He slammed on the brakes, then he started to get in the right lane. As I went to drive past him, he came back suddenly into the left lane, cutting me off, forcing me to jam on the brakes. He then did it again- going into the right lane, and then swerving back to the left lane in front of me as I tried to pass him, and then he slammed on the brakes. He went back to the right lane a third time, and I passed him. At that point I decided I was going to stay calm and look straight ahead, and if he came into my lane and hit me it would be his fault. I passed without incident. I did not flip him the bird or anything as I passed, I did not want to give him the satisfaction

Was I wrong for giving him the brights or was he wrong for trying to run me off the road?