Internet Dehumanization

I was playing Call of Duty 4: Modern Warfare online the other day when during one of the matches one of my opponents sent me a message: "ur a f@g." Seriously? Somebody took the effort to do that? What is the world coming to? I wanted to respond with something clever "Wow! How did you know such bad grammar would piss me off so much?" or "How did you know! Are you alone in your room right now? Can I come over?" In the end I figured that is exactly what he wanted me to do so I restrained from replying. Still, it really annoys me that someone would do that. Why? To what end? Does he lack self-confidence and have to try and make himself feel better by putting others down? This also begs the question if we were playing in the same room together instead of over the internet would he have said the same thing, and if so would I have the same reaction or felt of it more as a joke? I think this is just another example of internet dehumanization.