His reply wasn't meant to be witty, it was to make you think beyond what you presume. That message seems to have flown by at least two of you. Lucky for the rest of us, I had to click "show comment" to see what was written; at least there's a large group of broad thinkers.
I'm not offended by the image, neither by the comment, it's a joke. But, in my opinion it was designed to be what it is.