Glad to see some folks familiar with experimental psychology responding here. Desensitization to violence following exposure to media with violent imagery is a well observed phenomenon. The literature on the subject dates back to the 60s, with results replicated in literally hundreds of studies under varying conditions. As someone remarked earlier, it's hardly surprising, given that the military has used training techniques that rely upon desensitization literally since the dawn of time.
Articles like this just make the gaming community look silly. Attacking research as flawed based on the writer's experience of watching CSI is a non-starter. Making snide comments about how he needs to "keep working at it" and emphasizing that he's an Associate Professor (what, you need tenure before you're allowed to do research?) moves into the realm of unprofessional writing. Fine for a blog somewhere, or perhaps the latest Jimquisition screed, but out of place in an online magazine that usually adheres to a higher standard of industry analysis.
Bottom line, there are a lot of good questions we could be asking about the relationship between games and subsequent reactions to violence. For example, does the interactive nature of games enhance desensitization? A bigger question, not just related to games, is whether desenstization has a significant impact on subsequent behavior. Truthfully, that's still hotly debated, although it's hardly as dismissable a conjecture as some posters seem to think.
Intelligent debate and an understanding of the actual research out there is needed in the face of the hysterical Fox News "Do videogames make your children rape puppies?" articles, not simple "is not!" counterarguments.