The millstone that hangs around most people's necks tends to be financial and professional. The sort of psychic violence that comes from having to work for decades and follow an ever-growing social contract is far more harmful to our physical and mental health than any game. In this sense, gaming addiction is more closely related to the absence of a worthwhile link between effort and reward in real life for the majority of people.
The game industry is growing faster every year because the demand for an escape from the dull grind is rising just as fast. The violence is just a peripheral aspect of it.
Another aspect is that it's easier to recognize violence as fictitious. When you are exposed to real-life violence, it feels completely different from anything you've ever experienced in media. There is simply no confusing the two. On the other hand, sexual content tends to be more directly related to the act itself or to complicated emotions around it, even if the material is recognized as fictitious. Sometimes the content IS the act, if we take into account that for a large number of individuals the main draw is the exposure itself.
Unlike with fictitious violence, the tastes of the player/watcher/consumer are in plain view, and we know that these tastes can then easily become behaviors. Much more is revealed than we would care to see. That is why is it considered much more abhorrent.
