However, we don't have infantry who can be killed, even though they may have gotten lucky on rare occasion. We have tanks with guns which can't be disabled without taking the entire turret out, without any regard for realism in that particular area. What other weapons are immune to similar weapons? You can get your guns shot out while in a bomber, fighter, or attack plane when shot with just about anything, and the same is true for half tracks, amphibs, ship guns, field guns, and PT boats, but not for the MG up top on tanks.
Interesting story on Mr. Pillsbury, but I don't think using one-in-a-million lucky shots as an example accurately depicts a vulnerability of all pilots in ground attack aircraft. Anyway, that's off topic, since the issue here is that the gunner can kill the pilot, but the pilot cannot kill the gunner.