Playing the devil's advocate a tiny bit here, but Isn't it funny that you're accusing him of not giving a valid argument and just spewing ad homs when both of you are basically doing the same? All I seen from both sides is basically:
"Hurr ur dumb, me smart."
"No ur dumb, me smart!"
"ur dumber u dumbdumb"
"haha ur wrong, ur dumb and your mother"
"u look like a chipmunk hurr"
"dumbdumbdumb, so dumb"
"lol look at my dogs also ur dumb"
"no u!"
Now either go full out with the flaming or not bother at all. Trying to intellectualize callouts just makes it look more.... dumb.