Why is it okay here?

For some strange reason I was thinking about griefing the other day. "Griefing" - going out of your way to ruin someone else's time.

In what other games and hobbies is griefing okay?

Killing someone in PvP fine. But corpse-camping them? Going out of your way to wait until they rez only to kill them again?

I remember why I was thinking about it now. Someone went out of my way to say some nasty things to me.

At least I got over it quickly, but it makes me wonder why that behavior is tolerated.