I think you did a great job with the old lady that stopped & turned. She passed the group, I assume at a safe distance to not get anyone upset over that. She used a turn signal so you spotted a potential worst case scenario where the motorist freezes, you took the opportunity to determine the lane was open for going around the car and left enough time and room to go around without an incident of anger. Heck, stopping yourself on a bike wasn't even a big ordeal, inconvenient, but you have to figure at the very least the old lady has poor vision, can't judge depth, speeds & whatever else necessary to have not even agitated the other cyclist(s). I can see the other guy's moment of frustration, but he got upset and yelled at someone's grandmother. So he really didn't accomplish much and there are other ways to express dissatisfaction.