Why do people always try to act so tough on Call of Duty Online games?

Black Ops, MW2, COD4. Whatever online FPS and stuff. 8 year old kids or not. Why do people try to act so tough online? Geez.. It's only a game. I kinda just laugh it off. Just because they can say "n*gga and f#ck this and that with death threats" it apparently makes them super tough online. I got this dude really mad at me once just through playing and then ertive talking him, he went on to say about how he was a "G" and that he would find and kill me because he's a millionaire and he sits on a golden throne? I kinda just cracked up.. So really. I usually don't meet many people like this on the streets. So why with all the aggressiveness?