If i as a non CC, but with some healthcare knowledge may comment:-
Personally i would have taken the decision to offload the poor woman, all the reasons above are valid but i would have based the decision on purey healthcare grounds. she should have recived proper healthcare BEFORE boarding, most airports have a medical facility of some sort and they should have been called in by the check in staff. i belive they lacked in their duty of care for the passenger. the Captain made his decision on his duty to the airline for meeting slot times and not incuring delays, the CC decision was based on their prime duty to ALL the passengers. the others for their health and wellbeing and the woman and son for her health and medical needs. she should have been offloaded and given PROPER medical care and put on a later flight. this woman had open puss sores and also would probably have had abcesses that had yet to erupt, these would have swollen and become rather painful as the aircraft de-pressurises. i belive that the CC made the right call, well done tuismile, hope i fly with you some day, I'll be in safe hands.
all the best.
Greg
Greg