My advice to you is to adapt, improvise, and overcome. This is an old saying (which I first heard during my stint in the USMC) and is actually a good one. If one of the opposing teams has a sword, switch your secondary weapon (or you main one if you want) to a shotgun, or if your teammate is closer to it, have him/her do it. Another thing you can do is just pick it up, move to another part of the map, and switch it out for another weapon so that they have to search for it. Or you can use it. Also, the only games that should give you trouble with the sword are AR starts. A DMR is a 5 shot weapon, and between the two of you you should be able to take out sword guy fairly quickly. Remember, first 4 shots in the body, last one in the head. http://www.bungie.net/Stats/Reach/FileDetails.aspx?fid=23085127&player=AAN2 this is a video of me taking out a guy with the sword and sprint using a DMR. The guys shields had JUST regenerated, and I still managed to survive. So, the sword isn't an almighty weapon, and if you actually strategize you should be able to kill someone holding it rather quickly.
And remember, if someone else beats you with it, and you can't beat them with it, it means you have to get better. And you don't get better by complaining about it.