I like that one. In a similar vein, these two both paraphrased and attributed to Mark Twain:
"Arguing with an idiot is like wrestling with a pig in the mud -- you both get dirty and soon you realize that the pig enjoys it."
"Never argue with stupid people. They will drag you down to their level and then beat you with experience."
Also related, but unattributed:
"Lions don't lose sleep over the opinions of sheep."