Sure, he appears to be quite incorrect now, but dismissing a mind of the caliber of Dyson’s because he got this one thing wrong is pedantic. And yes, he did appear to get this one extremely wrong, but that should not overshadow his amazing ideas and all of the things he got right. Ideas like Dyson Spheres, nuclear explosion based space travel, and many other Dyson ideas were just as outside of the standard deviations of thought as climate change denial at the time he came up with them.
It appears extremely popular right now to disregard an entire human’s work over an apparently incorrect opinion. Freeman Dyson is a great example of why this is probably a bad idea.