*Shrug*
Ignorance is inescapable. Whether you're disappointed about it or not, not every person is not born knowing everything they "should" know. To simply condemn someone for not knowing something is effectively elitism. Unless their intent was to do harm, or they refuse to be educated and change the error of their ways, they've really done nothing wrong.
I'd always thought quotes and other small things were public domain, since politicians and media quote on another consistently. Professors quote dead geniuses left and right. I've even seen profitable, copyrighted material uses quotes from real people. Since no one's ever taught me the finer points of grayer legality, I didn't know.
But on a similar train of thought; if its possible to copyright something as short as a quote, I wonder why people don't simply place trademarks on popular memes and sell them? Or why people don't place sole ownership on their own (embarrassing) quotations to stop the media from ridiculing them?