In short, you might be using the word according to its most controversial meaning, whereas those you criticize are using it for its most widely accepted meaning.
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verb: decimate; 3rd person present: decimates; past tense: decimated; past participle: decimated; gerund or present participle: decimating
kill, destroy, or remove a large proportion of.
"the inhabitants of the country had been decimated"
drastically reduce the strength or effectiveness of (something).
"public transport has been decimated"
kill one in every ten of (a group of people, originally a mutinous Roman legion) as a punishment for the whole group.
"the man who is to determine whether it be necessary to decimate a large body of mutineers"
Destroyed a large part of it, or destroyed a small part of it?"
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