How can people be shitheads on PvP?
The only way is if they group up against you solo or if they play an overpowered class in 1v1.
Griefers are usually bad players, you can beat them easily.
But yeah some people are trolls.
Just the other day, my ilvl 348 rogue was getting one shotted by a Monk with 80k health in BG's.
And he proceeded to login on a different character and whisper me. Asking me if i was mad and saying he was an incredibly skilled player. LOOL
I thought it was funny though