[gregjor]

> then I am also free to decide that those views are absurd and extreme, and reflect a deep misunderstanding of medical outcomes.

I don't agree. You can decide that another person's expressed opinions don't align with yours, according to what you believe and think you understand about medical outcomes. The original comment didn't mention medical outcomes so I hesitate to judge how much the commenter knows about that. And I hesitate to call someone's personal views absurd. They have opinions I may or may not share. I can't make a rational argument to prove them wrong.

A person's beliefs can't "be" foolish or even wrong. Belief by definition does not come from an objective and rational evaluation of facts and probabilities. I can say I hold different beliefs, but no more.

We most often encounter this kind of argument around religion. Someone can sincerely hold religious beliefs that don't submit to rational and objective argument. We can have different beliefs but we can't prove someone else's beliefs wrong. To call a belief that you can't argue against with reason "foolish" or wrong equals calling the person holding the belief foolish and wrong. You can show that chemo can work and people with cancer can recover. You can't say how any individual should feel about that, or how they should choose to deal with a cancer diagnosis. The original comment didn't make any statement about whether chemo works or not, or whether some people can thrive with dignity after losing a limb. Rather the original comment expressed one person's belief about how they feel about those possibilities, for their own definitions of autonomy, dignity, and quality of life.