N1K2s hurt people's mental pride.
1) No doubt, some planes are easier to fly than others. Planes like the Spitfire MkIX were known to be excellent and pleasant to fly in real life, and it is the same with AH. Pleasant and excellent.
Now, what I've noticed, on-line games playing against fellow human beings, are inevitably highly competitive. We thrill in the victories, and are angered in defeats. When this comes to something like AH, when you are beaten by a plane that is easy to fly than yours, you sometimes need a process of self-gratification to ease your anger(which is in truth, most cases, being angry to oneself) - "I didn't lose because I was less skilled. I lost because the guy had a better plane than me. If we were flying the same thing, I'd have won."
It's a pride thingy.
2) The N1K2 is an excellent plane. While it is not fast enough to dictate the fight, it makes up for awesome firepower and maneuverability. Planes like these are very difficult to catch without careful concentration which requires time - time which one often does not have enough in MA environment.
So, the story goes like this: There are my buddies and enemies fighting. We almost win, except this one guy in a N1K2 moves around, attempts HO, gets a lucky hit and drops our guys like flies. It's an angering sight, and we are determined to make the "dweeb" pay.. except the damned thing turns and dodges so good that it takes time. The fight drags on low, and by the time we are one second away from killing that N1K2, the enemy reinforcements arrive and shoots down all of us. We get mad, and we naturally blame the "fediddlein' " N1K2 for our mistake in SA and over-ragedness.
3) The N1K2 did some weird things in previous versions, and still does some weird things. Sometimes its performance is so good that it defies our conventional calculations and estimates. You do this, think there's no way a N1K2 can follow you, and then *pow* You turn out to be wrong, and you are shot down. To think that you, a guy who took months in mastering elaborate tricks and E-calculations, have been shot down by a super-easy-to-fly plane piloted by a guy who knows nothing but up-your-6 stick pulling.. hurts your pride.
4) Some people, or some squads specialize in the N1K2.. and often they are recognized for doing "dweeby" things. Most of them are excellent pilots, too.
Now, if there was a good pilot, who used a "hard" plane, reaching the level of excellency despite all the handicaps, people will look up to him and respect him. But when you see a pilot who would still be successful even if using other planes, stick to the N1K2 or Spit9 and rack up huge kills, naturally you begin to detest him. Most of us expect "character" that coincides with "skill" in a persona - the more skilled you are, the more character you have, and more modest you behave.
Somehow we think those people will limit their own greatness, or try and achieve great things with a handicap given, rise up to the challenge... but when we see a person with great skill sticking to easy stuff, we assume that "he's a schmuck". It's like the US Olympic Basketball team - 'dream team'. All the other world's playes are under-paid, under skilled amatuers, and this 'Dream Team' formed of multi-million dollar players with NBA skill-level rips apart all competition. People from other countries resent that.
Seeing an excellent pilot run at every disadvantage, come back with huge reinforcements, plow through the battle in that N1K2 and score two-digit kills, and then become the first one to run away at an impending crisis leaving all his team mates behind.. that disappoints a lot of pilots.
...
So, all-in-all, it's mostly a mental thingy.
