This isn't usually an issue... But I see where you are coming from. Until the no spawn camping rule is enforced, however, best you can do is push them around as a pyro, taunt lock them with a huntsman, or get another donator to block all of their fire using godmode.
And report it here. Major offenders will probably be taken care of pretty quickly. Trade Hell is supposed to be for trading, not playing. So the points and dominations don't really matter to most people. Though I do agree that a certain godmode asshat can ruin the experience for newcomers and veterans alike.