So are you idealistically opposed to evolution of language by repurposing of words? I've always found it an interesting debate...correctness vs popularity. In this case, the root of the word (dec...ten) makes it obvious the "correct" usage of the word as you point out (I also didn't know that that's what "decimated" means, thanks for pointing it out). So I tend to agree with you there.
On the other hand, when defining language itself, all I can really come up with is "a generally agreed-upon form of communication." If enough people agree that "decimated" means "destroyed" (as I thought it did), then doesn't that in itself morph the language?
Then there's the big-picture view: the language is going to morph by general consensus whether or not I agree with it.
For some words, I prefer to cling to the last vestiges of the archaic definition until there's nothing left. And "decimated" is too cool of a word to, er... annihilate the original meaning.
I think a solid case could be made that 10% of the original meaning is left.
If you really like the original meaning, then you should increase its usage in as originally meant so that there's a reason for dictionaries to place the original definition next to the ones that other people actually use in real life.
On the other hand, when defining language itself, all I can really come up with is "a generally agreed-upon form of communication." If enough people agree that "decimated" means "destroyed" (as I thought it did), then doesn't that in itself morph the language?
Then there's the big-picture view: the language is going to morph by general consensus whether or not I agree with it.