Dawkins is not wrong, hes using logical reasoning.
If a person doesn't believe in evolution, that means they believe organisms do not change over time. Which means they most likely believe in creationism. in the US, 80% of the population are christian, which means the 60% that don't subscribe to evolution probably believe the genesis creation story.
If you believe in the genesis creation story, and that everything magicked into existence because of the old testament god, that means you believe the world is only 6,000 years old.
He doesn't need polls. Its obvious. if 60% of the US population is retarded enough to think evolution is wrong, then they are retarded enough to believe the world is only 6,000 years old. These stupid beliefs are interconnected.