Why would I want to harm anybody else all because of my misfortune.
How about those who deliberately create that misfortune?
While you can’t fully control whether or not you get cancer, the cost of cancer treatment doesn’t have to be a “misfortune”. Cancer treatment doesn’t have to be out of your reach. Every other major world power has figured out how to fund universal healthcare.
The people demanding that you bear the artificially inflated, exorbitant cost of treatment are calling for your death. They are attacking you. They have figured out a way to literally murder you with institutionalized neglect. That isn’t hyperbole; they are running a protection racket, and using your death as a warning to others thinking about not purchasing their services.
The victims of such attempts on their lives should have no moral qualms against causing harm to the entities responsible.