I don't know all the particulars of IQ distribution but I do know that it's controversial to say that it accurately measures intelligence. Carlin was talking in vernacular and so I think it's safe to assume he was not necessarily talking about IQ tests.

Even though IQ is designed to be normally distributed do you really think it actually is a normal distribution? It's a lofty goal and I'm sure it gets as close as one can but does this perfectly match up with reality? I have my doubts, hence my claim that there's a decent chance Carlin's comment is wrong.

Yes, median and mode are averages but few people mean those when they say "average". I doubt Carlin was statistically sophisticated enough to use average instead of median. Had he meant the median I think it reasonable to assume he would have said median. Do you commonly say "average" when talking about the mode or median? I doubt it.

Maybe don't be so quick to criticize next time.

Perhaps we could both benefit from this sage advice.