Yeah, i think the crucial point in all this was that, whilst it fit under the seat if it was sticking out in anyway that could cause someone to trip in an evacuation, it shouldn't be stowed under the seat in front. Although I sympathise, it was absolutely right that the bag was offloaded. Tagging and offloading bags is a hassle for the crew so it is unlikely that they would have done it if they really didn't have to.