You'd be surprised. In the past I've frequently been floored at the lack of understanding exhibited by the people I've talked to, over relatively simple things that should be well within the fields of their own expertise.
The funny thing here is that so many people immediately thought of that as a purely scientific term, not at all realising that it was only a metaphor in this case. I wonder how many people here even realise when they speak metaphorically, use simile, analogy and what differences are, and the subtle differences and true meanings are of many of the words that they use all the time...?
I wouldn't claim to even be aware of all those that I myself use. The thing is, communication isn't a straight forward science, it's an art and anybody can get it wrong.
someone shouldn't apologize and think of being a racist just because someone doesn't understand the whole concept of black holes or white boards(cause you use pens of color to change the whiteness :P)