Camping is a problem because, in real life sniping is like that hard-ass 'Ghillies in the Mist' mission where you play as Cap. Price in CoD4. You take ONE SHOT and then you RUN THE FUCK AWAY.
Why? Because everybody knows where you are now, and they want you DEAD!
Therefore, campers who are successful are in a position that gives them an unfair advantage because of poor level design. Sure, you can say its strategic, but I can say its annoying as fuck.
Its stupid for people to demand realism from their video games, and then complain about how they can't do something that's not realistically possible. If you ask any real life military tactician, you will find that none of them will say that staying in one place for an extended period of time is a good idea. You need to be mobile, or the enemy will outmaneuver you. However, camping doesn't have that problem, so saying its realistic is like saying gravity only works when you're jumping.
Also, if there was a game where everybody camped, it would be the most boring game of all time! Nothing would ever happen because everybody's waiting for that "noob" to come around the corner.
Lastly, and this may not be fair to the rest of you not-quite-so-douchey-campers, but you will always, ALWAYS, be lumped together with spawn-camping fucktards and the other douche-berries that take advantage of glitches in the game that make them near-invincible.
As The Heavy from TF2 would no doubt put it, "CAMPER IS WEAK LITTLE COWARD BABY!!!"