Both my parents have now died of cancer and I remember this being a term that irritated both of them since the first cancer diagnosis in our family in the nineties.
It's now used for loads of illnesses, including an autoimmune illness I myself have, and I still deeply dislike it. It just seems geared towards trying to make people shut up and not talk about the distressing sides of shitty illnesses - because "fighters" are brave and dignified and tough, right?
And I know it's just one of those things that people say without thinking, but by calling someone a fighter you are implying that there are also people who are not fighters, who are obviously doing illness wrong. It all feeds back into the way people who are not healthy try to rationalise devastating illness and death, and comfort themselves that it will never happen to them or their loved ones. But everyone dies, eventually. It is not a character flaw!
Why is this still inane "fighter" bollocks trotted out so much at people who are sick and sometimes even dying?