Ancient Jedi showed the ability to do this to offenders. Since the jedi already believe in capture, and this ability IS possible (and no, it was not blocked in the series thus far, so why should we assume it can be blocked?) it would make sense to strip potential dangers of the Force to -preserve- the balance.
Why? Because it would the ultimate technique and it would defeat everybody, if it could really do what you would claim then the Jedi would have learned it into perfection its the only logical thing to do.
The better question would be, "How can they defend OTHERS with a lightsaber?" The Jedi are better off thinking less of their battle readiness and more of how they can use the Force for good and can defend others, to uphold the jedi ideal. Winning a fight can still lose a war, you know.
Idealistic bullshit. There is no way the Jedi can stand up against a threat like the Sith without weapons. A lightsaber is the perfect weapon. Its quick its precise and it allows you to use none deadly attacks sometimes. A gun would never allow you to do that. Without weapons the Jedi would be dead.
Hand to hand fighting, against somebody with a lightsaber? No way in hell you are going to win.
They also identify you, are harder to use in certain area's, are harder to take with you and weigh more... Lightsaber is a better weapon, and you will less likely have to use it because you can hide it. Coming in somewhere with a weapon and you are going to fight faster.
Disarming? Well isn't that what they are supposed to do with the lightsaber, besides it has a few other functions besides killing as well. Few as they may be they are still there. Nothing would work as well as a weapon like that.
Dooku disarmed Obi Wan and Anakin twice. okay he was a Sith but he wanted them to live showing that it can be done. Mace disarmed Sidious then decided he wanted to kill him. Anakin disarmed Dooku then killed him but still it shows that it can be done. Its what Jedi are supposed to do.
Okay it wasn't done against the clones but the clones can't be left alive. Seriously you know this.
And like USH said, they are more like Crusaders then monks.