I'm not sure one has to play a course, but certainly one should see it.
Around these parts we often get commentary posing as expert opinion on courses where the self-appointed guru has never even seen the course or property in three dimensions. That too me is absurd.
I do think folks can comment on course from television, or from pictures, and I'd hesitate to ever try to stifle those commentaries, as long as they are approached from the standpoint of the caveat that, "from tv (or the pictures posted here) the course seems to be X....etc.".
But when someone posts a drawing map of a course, or better yet, an aerial of the course from 10,000 feet in the air, and then purport to tell us why this was or wasn't a good golf course, or more ridiculously, attempt to compare it to another course they've never seen, then I think we have to just call bullshit.