I find the people that whinge and whine about snipers in general are either those that a) cannot use them themselves, or b) don't know how to adapt to play against them. They're not something that can just be picked up and played with and expect to get kills.
Which games are we talking about here, because in the vast majority, it seems that's
exactly what makes sniping such an attraction for so many people. The ability sit well out of striking distance and take time to aim at your targets with a large clear crosshairs makes sniping in most games comparatively easy.
I agree with your point if the game incorporates proper ballistics and gun mechanics, but there are few that do this, and the ones that do aren't really likely to attract the sort of gamer for who a good KDR is important. BF3 has bullet drop, but it seems to be relatively simplistic and on a lot of maps, not even relevant with the bigger rifles. You can aim and shoot with relative ease, at a magnified target who (should be) unaware of you.
That's why people flock to the sniper rifles in games. They forget that there is far more to sniping properly than just being a good shot (knowing when to shoot and when not to, relocating so you aren't discovered, etc) and think just because they've picked up a rifle with a scope on it they are suddenly the next Vasilli Zaitsev.
I'm not having a pop at people who enjoy playing with sniper rifles, but I don't think it's fair to make out that it's somehow incredibly hard to do in a game which doesn't model all the things which make it such a precise skill in the real world.
EDIT: This argument probably wont apply to games like CS - although it's easy to aim and shoot a sniper rifle in these games, you're often duelling at much closer ranges rather than keeping the enemy at arms length.
Agree that a good sniper is essential though and for those spitting bile at the one who play a proper "sniper" (or camper, as you call them), you'll be glad for their use of concealment when they take out the machine gunner who's pinning you down. Many a time in RO2 I've been indebted to the skills of a good sniper providing support.