Confusion about the implied repetition (or not) of an adjective in a parallel construction

"I hate hard candy and olives" can have both those meanings. That's the beauty (and the curse) of the English language.

I would say that "I hate olives and hard candy" is definitely less ambiguous, but it's not any more or less concise (after all, it contains exactly the same number of words).

Whether an adjective applied to the first term of a parallel set of nouns also implicitly applies to the second is as much a matter of common sense as anything else. It certainly isn't automatic, which is why, for example, the sentence

I hate hard candy and helium.

is unlikely to leave many readers or listeners puzzling over what "hard helium" might be. Since "hard candy" is widely recognized as a way to describe a particular thing, and "hard olives" is far less often encountered, I would expect most readers or listeners to treat the noun olives as unrelated to the adjective hard. Indeed, a sensible writer or speaker would be sufficiently aware of the oddness of "hard olives" to recognize the usefulness of repeating the adjective hard if that combination were what he or she had in mind:

I hate hard candy and hard olives.

That's not to say that the adjective never logically applies across parallel nouns. For example, presented with the sentence

I hate polka-dotted shirts and pants.

most readers or listeners would surely suppose that the objection is to polka-dotted shirts and polka-dotted pants, not to polka-dotted shirts and to pants in general. Ultimately, the logic of the sentence provides the basis for interpreting the intention of the speaker or writer—though some instances may be ambiguous enough to justify reordering the term to avoid confusion. For example,

My favorite art forms are black-and-white photography and collages.

might better be rendered as

My favorite art forms are collages and black-and-white photography.

if color collages are included in the person's collage appreciation. But in general there is no need to structure your sentences so as to accommodate a grammatical version of the distributive law of multiplication in the face of common sense.

I would rather have seen the writer composed the sentence as such "I hate hard candy, and hard olives. This way the reader would grasp a clear image in mind without any confusion.