There's no more satisfying kill than shooting a attack-chopper dude out of his Cobra,you can really feel how pissed off they usually are (You can't see what he's typing because he's dead but you can see the language filter warning ).
After 2 kills(sometimes I get them a second time on the helipad,Midnight Sun is awesome for that!) the pilot usually hunts you down personally - could there be a better contribution to the team?
One sniper keeps the attack chopper(which usually rapes the shit out of spawnpoints) busy by playing hide and seek with them.
On Midnight Sun somebody tried to hunt me down with the Chinese Recon chopper - and he lost the duel against a M95(no headshot,I pumped 2 mags in it and BOOM!).
So I guess people hate this kit because of things like that,maybe they can't hit squat with the sniper rifles(but secretly wish to) or they are annoyed by getting headshot after fighting off a couple of assault-guys.
Nobody whines about jetwhores anymore,they just rape away,but when you kill somebody unexpectedly and skillful with just a rifle people want personal revenge,if they are unable to do so they flame in the forums how useless snipers are and other bullshit.