I do seem to recall a challenge from Urchin to Toad, in which Urchin's argument was along the lines of Karnak's, and Toad's argument was along the line of everyone else. IIRC, Toad failed to shoot down Urchin's bombers.
Ofcourse, this once incident doesn't prove anything, but it does give you something to think about. Maybe it's just that the "buffs are easy to kill" guys never really meet people as experienced in gunnery as themselves manning the defensive guns in buffs. I mean, usually people who fly buffs are not really the 'vet' sort of people, and all.
Maybe the vets who feel confident in both gunnery and flying skills should get together and actually test it out to see how often one can so 'easily' shoot down buffs that are manned by people actually as skilled as theselves. Might be interesting to see how the results come out.