That was a pretty stupid dangerous thing to do regardless of the fact he was tailgating you. Not only his life that was in danger but a car coming in the other direction who is a totally innocent party could have been involved.
Some guy tried to cut me off in the rotary yesterday. He was coming into the rotary and I was already in it (meaning I have the right of way), and he didn't stop. I just kept my speed and leaned on my horn and the douchebag had to slam on his brakes while I just kept going