Camping is a cheap, stupid tactic. Stop trying to justify it.
So it IS a tactic? Because running and gunning is also, but often a bad one. In fact, I think its largely stupid. It may have worked (and was kind of the point) in games like Quake III, but not nowadays. Mechanics in multiplayer nowadays(especially CoDMW2) are made in an attempt to force intelligent play.
And there's that word again, cheap. What is cheap? From what I've gathered, cheap in this context refers to the use of tactic that supplements a "lack" of "skill." The problem here is the definition of "skill." Not everyone is a twitch gamer, and at the end of the day, the "camper" who isn't a Ritalin poppin 15 year old (forgive the stereotype, it's to make a point)
is the one outsmarting said 15 year old. I believe the most reasonable definition of skill is the ability of one the reach the goal of the match being played.
All the above said, I can run and gun. I just don't like to. It hurts my k/d, and it's not intelligent. I play intelligently, even in team death matches, when the only goal is to kill the other team. If this means holding a building that is a strategic boon to the rest of the team, or just so that the other team CAN'T have it, so be it. If it means keeping an eye on an area that the enemy team seems to frequent, I'll do that too. Its up to the other team to notice this and adjust accordingly. If not, then that's their mistake.
Also, whose ass did you pull that "90%" from? Was it a survey? I doubt it. While yes, some people will just one sit at one point for a relatively unreasonable amount of time, getting the occasional kill, you should have the intelligence to realize that they aren't helping themselves or their team. While they're doing this, the rest of their team is one man down in whatever coordination they may try to pull off. Further, like MANY others here have REPEATEDLY pointed out for the benefit of those such as yourself, there are ways to render the rooted camper useless, via outsmarting him or just avoiding where-ever he/she may be, which nowadays is more or less ALWAYS an option. If you can't figure that out, that's YOUR handicap, like your supposition that campers are somehow beneath your ability to run around in the open, presenting your head to whatever sniper may be waiting for the opportunity.
As for justifying it, I don't have to. In these kinds of games, I'm here to kill you, not to play by your definition of "fair." This likewise applies to weapons that are somehow labeled as "noobish." I believe your argument functions on the assumption that the only kind of camping is "corner" camping. That's not so. The "good" kind of camping, the strategically sound one, occurs when the other team doesn't even realize that you ARE camping.
Edit: And please don't misunderstand me. I don't camp the whole game. I do alot of running and gunning from area to area. Like any good strategy, it depends on what the situation calls for. The anger I do feel at the people who sit in one corner for the majority of the game is more often than not misdirected, which should rightfully be pointed at myself for falling for it more than once.
Also edited for the sake of clarification and grammar.