Cluck,
You are allowed to fire if your hog is moving and your driver is not violating any of the racing rules, which he was, so you should stop gunning and hogchat your driver to go to his navs.
Your driver was the one breaking the main rule, but you're sort of aiding and abetting if you also gun when he's chasing.
If you simply say "driver I'm not gunning until you stop chasing and go to your nav" ... problem solved. It's fairer to the other team, and it gets the message across to your driver so he'll stop.
6.7. You may fire from the gunner's turret, or fire or grenade from the passenger seat, only if your hog is not breaking any of the camping rules. This means that the hog must be racing or picking up a passenger, and not chasing a kill. In this context, "racing" means:
Proceeding toward the next flag, OR
Driving to avoid being killed, while positioning to be able to resume proceeding toward the next flag.