Hmm OK, there might be some misunderstanding there because I'm not a native speaker, but in my mind it's a small step below "obliterated". If it also refers to just taking a small bite out of its market share, then my apologies for the misunderstanding.
No, you were right in the first place, RcouF1uZ4gsC was being pedantic.
Originally, decimated came from when the Roman army would conquer another group, and would assert dominance (and instill fear) by killing off 1 in every 10 soldiers. So it literally meant removing a tenth.
English has mutated the meaning to mean "nearly wipe out", which is very different from the original meaning. But that's common in language. Confusing.