Your counterexample would need to be a positive instance, not “other bad things also happen” and that evidence would also need to be strong! Chemotherapy has ma

Your counterexample would need to be a positive instance, not “other bad things also happen” and that evidence would also need to be strong! Chemotherapy has many terrible side effects but it helps kill cancer! With high certainty! You wouldn’t subject people to chemotherapy if you lacked any evidence that it was helpful.