The disclaimer is that they make money if people believe they are right, so may be inclined to cherrypick facts. So when we repeat Exxon Mobil's stance on global warming, we say that their stance might not represent all the facts. It's a disclaimer that this isn't my own opinion, and that I don't 100% trust it to be fair.
Nate Silver's reputation stakes on being accurate, so anything outside of a perfect result isn't great. This is different than Exxon Mobil's stance on global warming, where they make money when the truth about global warming was obfuscated.
