Don't let stupid win. The only power they have is what you give them. If you feel the need to respond may I suggest one of my favorites such as "Your level of comfort with knowing nothing is truly impressive" The goal is to make it challenging for you to find ways to insult them in such a way they spend the rest of the day asking themselves "Wait, was that a compliment or an insult?" See what I did there? Yes you too my friend can make an idiot think too. Have a great day and write on.