Had a guy entering I-95 in CT do the same thing to me. Held my speed. Not much choice really due to fairly heavy traffic. He had ample opportunity to speed up or slow down and merge properly. He did neither, just got to the end of the acceleration ramp and had to brake hard. He took umbrage at my actions and decided to teach me a lesson. He got around in front of me and slammed on his brakes hard. I slammed on the brakes too, and luckily avoided hitting him. My 9 year old daughter learned some new words that day. He then took off. It was our first trip with new trailer (F-150 and hybrid trailer) so I learned that I could trust my set-up fully. It was a hard lesson though. Also construction going on, narrow lanes, etc.
Where's a cop when you need one? Never have I wanted to see a guy nailed more so than that guy.