More importantly, did you know you can finish DX:IW without killing anyone? Or using a weapon at all?
Have you ever actually tried to play the game that way?
I have, and it's inanely frustrating and not very fun. Heck, if anything, it teaches you that violence is a simpler and more efficient method of problem solving, not to mention more entertaining.
Plus, IW was more Harvey's work than Warren's. Deus Ex? I dunno about you, but I was one violent mofo from time to time during that game. So being an invisible, cybernetic killing machine with a laser sword is fine ... but being a street gangbanger is not?
While they might be miles apart artistically speaking, to declare Deus Ex's violence as "good" and GTA's violence as "bad" is more ludicrous than the comparison itself. Hell, in Thief I would systematically assassinate people and hide their bodies so that I could better investigate areas. What, that's OK in polite society these days?
If people are going to get all pious about violence, they should check the color of their walls. Might be more of a glassy substance than it seems.
In his clarification, at least, Warren backs off on the violence angle and strikes more of an opinion about outdated genres and motifs in general. That's a far easier pedestal to take these days, although there really isn't a need to single out GTA for it.