I think this is a bit unsensitive to be honest. I have no clue how you interpret it, but personally I read: "If you can't do both, you're either incapable due to a physical handicap OR you're nor right in the head."
That's not how I took it (and when reading any forum, or critiquing in any medium, I beleive you should always default to the most favourable interpretation); I assumed that he means that anyone can learn to do anything, unless of course there is some kind of physical barrier to learning that task.
e.g. That if someone is "logically minded", that's simply a matter of their upbringing/training so far, and they could be taught to think/see in other modes if given the right learning situation (it's well known that people of different backgrounds actually think about and see the world in different ways, using different parts of their brain, and that this different modes of vision/thought can be learned). Something like a stroke may interfere with this, as it physically kills off certain areas of the brain.
We all might find learning certain things more/less difficult than others, and may need to learn them in different ways. Given the right situation though, you can be taught.
Now, there are technical artists, and artistic artists. There are technical programmers and artistic programmers. I lean more towards artistic in both cases.
This is kind of off-topic from your intended discussion point -- but in the industry, a "technical artist" is fairly well defined as someone who can use all the tools that an artist uses (like Maya and Photoshop) and can produce art with them, but who's job is to actually build extensions, sub-tools, scripts, importers, exporters, and pipelines for those tools, to help integrate the team's art assets with the game engine, and to solve problems that come up during art production. They apply their technical skills in order to make the art-artists more productive or more able to do their job.
What makes a good graphics programmer then? Do they have to understand art?
Graphics programming is one of the most processor-intensive areas of programming, at least if going for photorealism. At 1080p, there's over 2 million pixels that need to be calculated -- no other area of a game will routinely deal with data-sets of that kind of size. This means that a great graphics programmer must be well schooled in basics of computer architecture and computer science, and know many low-level programming tricks so they can write fast code.
They also have to have at least a casual knowledge of how art is produced -- they might not have to be able to create great art themselves, but they must be familiar with the tools and techniques that their artist colleagues are using. They need to be able to communicate effectively with these artists, as they are basically a supplier of technology with these artists as their client. Without being able to speak their language, then the specifications/requirements will be all wrong.
They've got to be curious about the world and have a technical eye for detail, but must also have an eye for art -- when viewing a beautiful sunset in real life, they must be able to critique what makes it beautiful (think colour palettes, framing, composition, etc) but also be wondering about what the underlying physical and biological processes are behind the formation and perception of those colours, and what kind of formulas could be used to model them.