Not to put words in his mouth, but I believe the complaint is that stealth gameplay originated as an alternative to the shoot-people-in-the-face mantra that had become ubiquitous to FPS and action games at the time. Indeed, stealth games became more about violence as a last resort - a desperate plea to silence enemies that could alert others to your presence. See: Thief, Hitman, and early Splinter Cell games.
Increasingly, though, "stealth gameplay" doesn't present itself as an alternative to violent play but rather "sneak up behind somebody and shank them in the kidneys." A lot of people mourn the loss of the idea of stealth in and of itself as a goal and play style, rather than just a fancier way to put bullets in people. Look at Arkham Asylum, the recent Splinter Cell game, Assassin's Creed... they're all more about using stealth to get close to people for violent actions (with the violent actions being the goal of the player) rather than getting through areas without leaving a trace. And these games aren't necessarily bad, but just as Rainbow Six Vegas sort of heralded the end of days for the seriously tactical FPS, Arkham Asylum may have heralded the end of "be completely unseen at all times" style of stealth gameplay.