Needless to say, I immediately thought of counter-scratching, "Aaaarghh! Your hate speech has damaged my delicate infant psyche!" I didn't, though, for several reasons.
For one thing, I don't have a delicate infant psyche. Another is that I do have a delicate lower back, which would have been the worse for wear had I attempted to bend over to pick up a stick and write a fairly long message. Also, the closest I come to scratching messages in the dirt is this blog.
Most important, though, is that I strongly believe in a person's right to be offensive. We can't have freedom of expression if we permit restrictions — any restrictions at all. I am willing to defend the release of "threats to our national security," every kind of pornography, and all varieties of out and out lies. We can choose to punish the consequences of such expression if it is shown to have caused harm, but we cannot allow anybody to decide in advance what kinds of expression might do so.
I'm not a censor, so I didn't kick away the message in the dirt. Others may have wanted to read it, either as an affirmation of their own beliefs, or for the giddy pleasure of feeling offended. Me, I didn't experience either of those. I just shrugged and walked on.