I sympathise with the way you feel, but here he did not refused treatment to better live the time he had left but chose "alternative medicines" instead. The discourse in those online communities is not that you should appreciate the time you have left but that they can heal you.
Those are two very different situations and while the outcome is sadly identical, they should not be conflated.
The sedatives and painkillers, are the biochemical discourse that you feel like you heal / healed.
When my father was dying from cancer, the doctors said his treatment was curative not palliative, which is essentially the same discourse you are offended with.
I'm not offended, I'm pointing out how the situation differs.
If doctors gives inaccurate information, it's an important problem that needs to be discussed.
> the doctors said his treatment was curative not palliative
In the present case, it seems like it was not the case: "At the time, Sean’s doctors told him he had at least a 50% chance of long-term survival if he underwent chemotherapy", while the alternative medicines gave false information: "Sean also relied on "thermographic scans" - heat images of the body" or "I’d use words like, 'oh no it’s the Herxheimer’s reaction'".
It seems to me like we are preaching for the same thing, which is to give the correct information to the patient and let him decide.