The grenade launcher requires zero aiming ability unlike the rest of the plaza weapons. People have pvp enabled, then as soon as you kill them they equip the grenade launcher and spawn camp. Even when you out-play them, they turn off pvp until they respawn, then just continue to use the grenade launcher. At least prevent people from re-entering pvp when they disable it, but the grenade launcher itself is also just far too strong to be a weapon in the plaza.
