Ya, you were being assertive and righteous ... and honestly, it might make them think. It's prob'ly similar to when a car decides to get out into the road in front of me and it seems they're assuming I'm going a lot slower than I am... once we're going the same direction I will accelerate so that I'm close to them and maybe they'll think I was even closer.
Yesterday the reverse happened... it wasn't clear whether a backing-out car had seen me or not and there was a car right in front of me... I'm thinking"yea, is he waiting for that car and going to back right into me?" ... and the driver put the car out of reverse so the back up lights went out, jes' fer me (I've done it myself...)