Why do some people claim it is forbidden by rules then?
I personally do not mind when they try to shot me down, if they are coming with the ball to score. It's a kind of strategy, and I never get pissed of by that. But oh, camping in the enemy base and trying to shoot down the keeper for ever. Now that's annoying.
Because people don't know the rules and make them up to suit themselves.
Here's what I do if I get harassed as the goalie. I see if the ball is far away (usually is around the enemy's team 'cause of all the retards camping mine ^^), pick up a high damaging weapon, go out, whoop their ass, then go back again, write in teamchat "We have some goal campers, I'll wipe them, but someone else take the goal meanwhile". If no allies show up, I switch between goalkeeping and wiping depending on where the ball is. If an all come, I see if they go for goalie or for defender, and I take the role they don't.