From Rabbi Zev Leff’s comments on Devarim:
Failure to see the mitzvot as an expression of the totality of God’s will, and not as just disjointed commands, leads to the distortion of mitzvot themselves. One year I received an urgent call just before Yom Kippur from a woman in my congregation. Her husband had been told by his doctor that he was suffering from a condition which could prove life-threatening if he fasted. Nevertheless he was determined to fast. I spoke to his doctor and consulted another observant doctor to confirm the diagnosis. There was no doubt that fasting would endanger his life.
I called in the man and explained to him that he must eat on Yom Kippur. He looked me straight in the eye and said, “Rabbi, you’re a young man and I’m about three times your age, well into my 70s. Since my bar mitzvah I have not eaten on Yom Kippur, and I do not intend to start now.” I replied that I could not force him to eat on Yom Kippur, but that as soon as he left my office, I would instruct the gabbai never to give him another honor in our shul. When he asked why he deserved such treatment for being strict with respect to Yom Kippur, I told him that we are prohibited from honoring idol worshipers.
“What idol worship am I guilty of?” he demanded to know. I explained, “The God of Israel has decreed that you must eat on Yom Kippur. If some other god has commanded you to fast, it is irrelevant to me if you call it Zeus, Kemosh or Yom Kippur – all idols are the same.”