It depends on the game.
In some games, camping makes a very easy way to kill people without them getting a chance to fight back.
For example, Call of Duty and Battlefield have guns and health-systems that mean you only need to shoot at someone a little bit and they die.
Which basically means that you piss off everyone because they have no chance to defend themselves, if you're hidden in a corner and can shoot and kill before they can even turn around.
On other games, like Halo, weapons are slightly less effective and things like Shields mean that it's much harder for someone to just kill anyone who enters a room solely by catching them by surprise.
It's much easier for someone who is surprised by a camper to turn the tide of battle and overcome them using other tactics.
I personally don't agree that Snipers should be punished for Camping, because that is what a Sniper does. They don't run around on the ground taking pot-shots at people.
If there is a sniper who is in a defensive position and he is dominating the enemy, then it's up to the enemy to attempt to eliminate him, either through means of their own sniping weapons, or through explosives, such as tanks, rockets or grenades.
If the game doesn't provide any sort of aid against snipers, then the game is poorly designed, and those people playing naturally as a sniper end up being unfairly punished and labelled as a camper.
For comparison, you don't often hear of the Sniper Class being considered a Camper in Team Fortress 2, primarily because the opposition always has access to sniping weapons by having one of their team take up the role of sniper.
Also, yes, ha ha.
We get that Camping has another meaning outside of games.
It was funny the first time, you're simply being anoying and stuff-posting off-topic now.