I was in a tank sitting 3 feet from the shore battery gun.....actually on the fortification sitting right in front of (and below) the barrel of the gun.
I duplicated the barrel position on the gun with my tank when I made my observation that a firing solution was available and confirmed with someone else that the gun was indeed occupied.
I also scored a couple of hits with the tank while this was going on.
I'm not sure when slapshot was there but that ship passed back and forth many times with the gun being occupied and not shooting long before my teammates were hip to the fact that the base was being attacked.
You may not be able to get the person out of the gun physically but them knowing you can identify them helps the situation become self-policing and will reduce dweebery such as this.
The other reason for friendly icons is so guys can call you on voice or text and tell you the position of a nearby enemy or vice versa.
I was there from the get go. I was one of the first at the base when it was flashing.
You may have thought you duplicated the SB gun position from where you were sitting, but could you really tell what someone sees in the SB reticule. Granted, most of the time, I was dogfighting those coming off the boat, so I couldn't know if the gun wasn't actually firing all the time when the CV was within a guns solution, but I did see it firing and I did see that it got a couple of hits on the CV.
Maybe when it wasn't firing, he might have been AFK or tending to wife ack and when returning, the boat was not hittable. I am not saying the you are totally wrong, but whoever was in the SB, at times, was firing on the CV group.