@Djinn, now I understand you better. Considering you are a writer, your revulsion is justified.
But in the age of the web, very often we take without referencing from someone else's writing or speech. It's bad manners at best but may not directly reflect their property management abilities. Note there's an author credited.
Anyway, as regards people, I always believe - Trust but verify.
PS. On a personal note I stand accused - always try to indicate references in quotes; but came across Oscar Wilde which got me thinking...
“Most people are other people. Their thoughts are someone else's opinions, their lives a mimicry, their passions a quotation.”