I don't agree with that statement. The ability to think critically or rationally isn't inherently tied to one's trustworthiness, in my not so humble opinion.
As much as I respect Vod--and I respect him a great deal--I think he probably shouldn't have left that feedback for the reason he gave.
Obviously joerogers8 is delusional if he thinks the Earth is flat, but I think his views on that are only loosely related to trust on bitcointalk. There are a lot of folks who hold some very strange ideas, including religious people. You could argue that Christians, Muslims, and Jews live their lives based on a book of fairy tales, but would I give them a neg on the forum? No, not at all.
However, Vod is entitled to his opinion and is free to give a neg to whoever he deems worthy of one. He's also the only one who can remove it, so this is an issue between joerogers8 and Vod. We can all give our opinion on it, but none of us can do anything about it.