C’mon. Still trying to rationalise? You do not quote without attribution. I don’t know why you drag this out. I made an observation, a valid one, and rather than saying something like “whoops, I missed that…” you tried to claim that as “well read people should know who said it…” you weren't obliged to provide attribution. Many people here are not well read. Many who have extensive reading experience might not have looked at ancient philosophers.
Lets forget long dead Greeks and segue (you like segues don’t you?) into something more modern. I am sure that more readers will be familiar with Harry Potter than Plato, so using your justification, how about quoting J.K. Rowling without attribution? That should be ok — shouldn't it? I’m sure that if she became aware of it, she wouldn't mind. Nor would her publisher or agent. If they do mind and “castigate” you, then they must bullies. Yes?
If Harry Potter fans get pissed off at you using their favourite author’s work without attribution then they must be petty minded and not very erudite. That how it works?