But the tone of the statement is always sarcastic since you’re expressing a kind of disinterested contempt.
We’re going to have to amicably disagree about this.
Fine then, I could care less.
I couldn’t either.
I don’t think the fruit/cheese thing is that hard to explain. Fruit as a collective is a mass noun, not a plural. “Fruits” pluralises this to mean “many collections of this thing”, like “blood” is a mass noun but we can say “the nurse took bloods”. What is impossible to explain, because it doesn’t make any sense, is why some things are mass nouns and others aren’t. “I’m going to buy some fruit” is fine, but “I’m going to buy some vegetable” is not, and there is no reason for this other than that “vegetable” just isn’t a word that works that way.
English is full of things that native speakers cannot explain. Why is it that “He dresses before going out” is fine but “I am going to dress” sounds weird and we have to instead say “I am going to get dressed”?