I totally get you, man.
I would respond to most annoying people as well. What this dude did though was so low it doesn't deserve a response. That's all I am trying to tell you guys.
Wasting your time on someone with such childish behaviour is unneseccary. Even if you make solid points it won't make you look good if you know what I mean. Besides it only drives most people more mad if you don't give it any attention.