So, basically all 10 had to draw straws, and the one that drew the shortest straw (you know, like the saying), was to be executed by the surviving 9 (stoning, clubbing,...). as all 10 risked dying and they still had to kill their mate, all were psychologically punished but only 1 died. (of course, if they refused, they all were executed).
To decimate is a very specific term in the roman army so 10% is the only correct answer (although it is currently used more broadly)
maybe clarify that it is the historical term, as the current meaning is both removal of 10% and removal of a large portion.
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?"