The reason is simple, because you just killed them.
- If you hard scope someone, you get trolled
- If you knife someone, you get trolled
- If you use a riot shield, you get trolled
- If you use a UMP 45, you get trolled
- If you use a rocket launcher, you get trolled
- If you get a ninja defuse, you get trolled
The simple cause of trolling on Modern Warfare 2 is that people will troll you no matter what. As soon as you kill them or humiliate them, they will find something to try and restore their ego.
People who have developed the knowledge of the mute feature and play for fun usually aren't affected by the trolls on Modern Warefare 2, or any other game by that matter.
Hard scoping is something of a controversial subject. I however hate the term in itself, as it is not a hard scope, it's a sniper kill.
In reality the controversy is something of an opinion, and how you look at the game.
Do you look at the game as a war simulator, or a game based on war?
//AC