I think his point is being missed. It's about quality of life and some of the horrible side effects of life extension efforts.
I get the rejecting colonoscopies and mammogram... because if it turns up bad news, you're looking at surgery and chemo... not so easy to take at any age - and hellishly awful when you're old. Not sure I agree about antibiotics... but I can see his point, and will be pondering it, about some of the other medical intrusions and treatments.
But then again - I've seen 3 family members go through the horror of chemo. Two spent their last days in the ICU with vents and pain and open surgical wounds from failed attempts to rescue them temporarily from a terminal disease. There is not dignity or quality of life in that. The third, my dad, did it on his terms. He died of cancer... and was taking an oral chemo for it, but not a horrible chemo. He died quickly when a cold turned to pneumonia which turned to septic shock. He was very afraid of the ravages of cancer, and the pain... and my sister and I believe that he somehow orchestrated this much more peaceful, and quick, death. He'd already buried my mother and brother after seeing them go through extensive painful lengths to extend their lives by days and months. (They were already terminal.)
My DNR is already filled out. I'm not sure about an arbitrary age... but 75 is about the ballpark I see as reasonable...