I think no one here can disagree with your first point.
As for the second, substitute low and mid priced cables with expensive and the same can be said. It's kind of a straw man argument.
As for the placebo effect, please. Once we have our systems optimized in our rooms and are very familiar with them, changes can be easily detected. I believe the placebo effect is only relevant when testing is being done, not evaluating in the long run.
As for Mr. Guttenberg, he's entitled to his own opinion and he's not the only reviewer out there with audio cred who believes otherwise, and is more convincing to boot.
The second thing he's quoted about re: cables having a minuscule improvement compared to moving speakers, room changes, etc. can also be said about amps, sources, and the speakers themselves. In other words, a poorly set up room will impart a poorly perceived result no matter the quality of the component. Swapping things out won't net you an improvement.
Also, the cables he has are in the price range of what I now believe to be necessary for a more than decent return on the money provided you can get them for less than retail. The Zu Event speaker cables I got were discounted from the nearly $1K price to just over half that and are outstanding in what they do. I'd never pay that much for cables but realize that at the price I got them for, they unquestionably better the ones I've use that retail in the $200-$400 range, including the Zu Missions, which I got the same way: on sale. With the lessor cables, it was a toss up as the differences were not major, just different, and I could and did go one way and then another. Passing that lower hanging fruit got me into the realm of what's possible.
All the best,
Nonoise