Yup, he was being a dick. But I've done the same thing to a fellow cager. I saw what she was doing, and I wasn't having her slot in front of me only to go slow as f*ck as soon as she did. I call it *dickmode* and everyone has those moments. She could have slotted in front, my grand marquis is slow to 50, but I honked and she moved back.
A bike I would have had no issue with. A bike would have been gone already.