As silly as it may seem, papers like this (and, in a lesser way, dopey sci-fi trash like The Matrix) cut to the heart of the monster of post-Enlightenment materialist ontology. "Science" tells us that "only that which can be demonstrated empirically is real"; but when asked to demonstrate the relationship (if any) between what we observe with our senses and the putative external reality, Science can only mumble, "I believe". After all, can any of us prove what we see, hear, smell, taste, and touch is For Real and not just a dream (or a computer simulation?) Nope. Ayn Rand notwithstanding, even the most hardboiled rational materialist must accept on faith not only that A=A, but that A exists at all.
In other words, the advent of high-fidelity computer simulation has slapped the smug look off the face of modern man and forced him to admit to what Aquinas, Aristotle, and Plato knew all along: that empirical "truth" is just another faith-based belief system.
Do we live in a dream or a computer simulation? No. Can we "prove" it? No again -- but we can know it. How? By direct experience. There are other ways of knowing besides empirical observation, among them direct experience -- the process by which we apprehend our own consciousness. We do not observe ourselves from the outside, empirically, watching with interest as we think and feel and do things; instead, we are ourselves doing all those things.
Even the most skeptical among us can, like Descartes, say with confidence cogito, ergo sum -- but we cannot demonstrate that fact scientifically. We must simply accept on faith that we really exist, and that the Universe really exists outside of us -- thus putting a lie to the pernicious idea that only that which can be "scientifically proven" is real.
And if we're going to accept that much on faith, why stop there?
I enjoy reading this kind of stuff, and it's a good thing if it makes the Average Joe think a bit beyond his next six-pack, but it's not to be overemphasized. My plan is to hide in the hills and wait until all the ExtropoFuturoTransHuman types "upload" themselves to computers -- then pull the plug and spend the rest of my lfe enjoying their stuff.
Empirical observation of the practical results of drawing the line there, that's why. You ask "why stop there?", but let me ask you this - if you're not going to stop taking things on faith there, why stop anywhere? Why not take everything on faith?