To be fair, consumer radios do use "AM" to label the medium wave band, so it de facto has dual meaning (regardless of the origin). It is unfortunate, but this kind of "misuse" of special terminology is rather widespread: for example we all often say "atomic" when we mean "nuclear." I agree that it is important for a general audience to be aware of the high-school physics, but to call an article idiotic for not insisting on it is not fair.