This is not "reportable". As long as he isn't violating any TOS, insulting players and so on, everybody is free to do as he likes. If you report someone not using his weapon in a way you like, you could also report fighters for not killing that last town building or not shooting at the enemy on your six.
And yes, I too was accused of "keeping the SB out of action" a lot, when in fact I was just waiting for the enemy TG to get into my arc of fire.
And why don't the player who are in the SB respond when another player are asking who is in the SB?
One time, me and some other players was trying to defend a base, and the CV came in the range to the SB, there was someone in the SB, but on range channel just shows me and the other players who i was flying with. Still the SB was occupied... A Bug maybe?
Anyway...... i see what you are saying, but the only player that don't whant me to use the weapon in the way i like are in that SB. The reason is that, he don't want me to sink it.