Actually, the poster is totally justified in trying to figure out how a lightsaber would work. For example, Lucas used the convention of Hyperspace, or extra-dimensional travel, to get around Einsteins general relativity. Lucas knew nothing could travel faster than light according to normal physics, so he tried to conceive of a plausible way aroudn that limitation, something that is already conceived of by scientists, although loosely. The point is, he made the effort to explain his universe.
This poster is doing the same thing in trying to explain limitations of a true "light" saber. Light can't reflect objects with mass, but an EM field could, the heat of plasma could go through metal, etc. It's also something that is already being tried in fusion reactors, it would produce that cool color, etc. As for other ways of making a high-tech sword, can YOU think of another conceivable technology that could reflect energy bolts with accuracy?
In fact, his explanation is so good it really should become the Star Wars EU reference standard.
You guys need to realize that if there is no plausible explanation for a device in a science fiction setting, it ceases to be sci-fi and becomes purely fantasy. If you don't need an explanation for how things work, that's perfectly fine, HOWEVER, some ppl like to think of Star Wars as adventures that might in the future some day be possible or nearly