Joe, I am not sure there is sufficient evidence from what you say to suggest that this is age related, rather than condition related. If airlines have a policy of not allowing ill people to travel, this would automatically disproportionately affect elderly people, because you are more likely to be ill when you are elderly. That is not automatically discriminatory and I can't see what evidence there is from your post to indicate that age was the predominant determining factor. It is also not true to say that MedLink would not discuss the situation with the family. They did discuss it with her daughter, the RN. They concluded she should not fly for 2 hours and once that conclusion was reached then stated that there was no further discussion merited. That is a different thing.
I am sympathetic. I do feel airlines have exploited the powers they now have, particularly since 911. There is most definitely a "sky nazi" attitude, exemplified by the infamous "AA orange juice" incident and the baby kid removed from a Continental flight for saying "bye bye plane". I am just not sure from the information provided that this is one of those incidents.