I didn't say it requires great intellectual acumen. In the blog post we're talking about, I called the argument "air-tight", "very simple", and "almost too clear-cut". I wouldn't have felt the need to explicitly state it at all, were it not for the fact that Eliezer and several other LessWrong people have been having arguments about whether veganism is rational (for a person worried about suffering), and about how confident we can be that non-humans are capable of suffering. Some people were getting the false impression from this that this state of uncertainty about animal cognition was sufficient to justify meat-eating. I'm spelling out the argument only to make it clear that the central points of divergence are normative and/or motivational, not factual.