The body requires glucose to function, yes. Certain cells cannot utilize ketones for energy; for instance, some are in the brain, the kidneys, and one other (I can’t remember). However, the body can create glucose via a process called gluconeogenesis. This occurs in the liver. How does it “tax the liver”? That’s a perplexing statement. Ask them to quantify it with information. Gluconeogenesis does not tax the liver. Alcohol consumption, toxic chemicals being ingested, very high carbohydrate diets, high serum insulin - these things tax the liver.
Also, you use gluconeogenesis whenever you can’t eat. I.e., when you sleep, you use it (and often ketones) for instance. So.
Ketoacidosis is probably one of the most misunderstood concepts in medicine. While it’s a state in which ketone levels are excessively high, it can only occur when you do not make enough insulin. I cannot overstate this: ketoacidosis only occurs when there is a lack of insulin. It does not occur as a result of too many ketones! Saying ketones cause ketoacidosis is like saying a cough causes pneumonia.
Ketoacidosis is a metabolic state that only occurs in situations with impaired liver function. There are only three instances I recall where this happens: alcoholic ketoacidosis from chronic alcoholism (tell your college friends to quit binge drinking), diabetic ketoacidosis when glucose is high and cannot be controlled by the body, and liver damage (for instance, damage from chemicals or other such things).
Information on gluconeogenesis.