I have to agree just a little with the writer, that D&D over-emphasizes hack-n-slash approach to RPGs over other kinds of gaming. But why else would you go into a dugeon to meet a dragon unless killing and looting were on your mind?
D&D can be played a multitude of ways, and much of that depends on what the DM and players want from the game. But, if you look at when most people are introduced to D&D (or nowadays WoW), in their teens, the game reflects what they are looking for in entertainment - obtaining and controlling power over others and their environment.
Many people into their adulthood continue to play the game this way - as Drunkonduty puts it, KIATIS. Several of my players, who have decades of experience playing D&D and other RPGs, tend to look at all encounters tactically (which ones do we kill first?) rather than as story elements. My other post on my player's meeting a blue dragon bears this out. They are woefully underpowered (7th level party vs. CR 14), but for two weeks via e-mail they were sorting out tactics on how to kill the dragon before one of them suggested they might want to parlay first to see what the dragon wants. They also count every little XP and gold coin that comes their way. And yes, I give out XP for "defeating" foes non-violently and uncovering important story elements.
A few years ago when I became dissatisfied with the KIATIS approach I found True20. It's option of non-lethal damage resolution and levelling up through completion of adventures helped me steer my then-players from looking at everyone they met as potential XP towards exploring story elements. GURPS is sort of the same, as combat takes so incredibly long that we might as well avoid it all together.
The Slate author does troll around in the article, but that's often what writers on this site are paid to do. Contrarian articles like this are to stir up discussion and debate. The passing of high-profile person such as Gary Gygax always brings about a lot of navel-gazing about our society. What did their life mean? What are the intended and unintended consequences of their creations? Obviously, from being a member of this board, I understand that Gary had a far more positive-impact on people's daily lives than many politicians and religious leaders ever do. He is the Steve Jobs and Xerox PARC of the RPG world. But even Steve Jobs' legacy one day will come under the same scrutiny as EGG's today, good, bad and indifferent.
If you want a more EGG-friendly articles, you should go over to Wired.com instead.