I know for myself I don't get many people whining on 200 or PMing me with insults after I kill them. I'm not the best stick but I do OK, I put myself into a lot of bad situations and I'm usually willing to fight anything in anything.
I think that when a pilot generally recognized as better than someone beats them, then there's not much whining. On the other hand, when a pilot thought to be of lesser skill kills one who thinks they're better, there's more likelyhood of a whine from the percieved "better" piolt. Again, speaking for myself, I let out an occasional whine when someone I don't think is that good beats me, but it's usually as the result of a cheap shot (HO, ack hugging, ganging, etc.).
When like pilots meet, there's a high likelyhood of the victor rubbing it in, even if it's a short one-liner. Again, for me, those are the most likely times that I'll get a 200 response and there's a few guys that do this regularily.
As to aircraft, obviously some are more challenging than others. For the most part, yes, you can use your strengths and play your opponent's weaknesses, but, between like skilled pilots this becomes more and more difficult until the point that, between pilots of equal skill, the one with the better plane will win almost every time.
Then there are the times where you can't play your strengths to their weaknesses; being bounced by a high con, getting ganged, etc. These tend to be situations where the pilot with the disadvantage feels slighted and becomes vocal afer their loss. People say, well, you put youself in that position but that's just not always the case. What starts as a one on one might quickly develop into a one on many with little forwarning. If the one also happens to be in a disadvantaged plane then, again, they will feel that the fight might have been a little more fair.
That's just a few examples of where people might feel frustrated to the point of whining. I don't think it will ever end. It's just human nature. If everyone followed a strict code of sportsmanship in the arenas then maybe, but that will never happen, however, the occasional whine/nudge in that direction isn't really a bad thing.