Here is a similar, but possibly easier to understand, example that would revolutionize/kill the sport of shooting: http://arstechnica.com/gadgets/2013/01/17000-linux-powered-r....
A later article (http://arstechnica.com/gadgets/2014/08/gun-linux-on-the-rang...) wrote:
"my photojournalist buddy Steven Michael nailed a target at 1,008 yards—about 0.91 kilometers—on his first try, in spite of never having fired a rifle before"
The first person using such a gun in shooting competitions would probably be called a genius in the sport, but soon every competitor would use it, and nobody would miss anymore.
The curling situation is similar in the sense that, if this were allowed, curling players no longer need to have good control of direction, speed, and spin of the stones they throw.
So it sounds like they make the throwing part of the game "obsolete" since the sweepers have so much control that it doesn't matter how bad the throw was. So it's unbalancing the game in unexpected ways.
side note, i think sport is too professional. And that it might actually be more fun for amateurs if they could curl better.
I mean we could have robots play the game perfectly and that would be a lot less fun... or at the least a fundamentally different sport.