i think you re-read before you butt in.
Dont need to. He said only stupid people will get the joke, while his IQ is high. This insinuates he's smart, which is why he doesn't get it, and you're mentally incompetent, and people with the latter trait will get it. That means people that get the joke would be dumber than him.
You then tried to flip his words on him by saying that all the people who posted and got the joke are smarter than him. This failed because to flip his words to say that, he would have had to have said the opposite; people who get the joke are smart while those who don't are dumb. He did not, however, so that shows you failed to comprehend what he wrote. The correlation(you not understanding what he said) and you getting the joke in the sig supports what he said. Mind you, I'm not taking sides, that's just what happened.