Aaah yes, the old "storage and zipper" intersection, built to accommodate more vehicles in a shorter timespan through an intersection. I use one of these everyday in my commute, and in my experience, drivers see the right lane (which eventually merges with the left, i.e. 'Zippering') as a 'passing lane', and speed along passing as many cars as possible before dangerously merging into the left lane. I always plant myself dead center in the right lane before approaching these intersections, and keep my eye on my rear view. Very rarely does another car follow me in the right lane for very long, as it is faster to pass a bicycle, and the drivers in the right lane are usually the ones in a hurry, and I have never been passed on the right. The driver you encountered sounds like either a real a$$hole, deserving of a tongue lashing, or a super inattentive driver, avoiding a collision with you. Either way, don't sweat it too much, and live to ride another day!