The main point of racing in any sport promotes the development of faster vehicles. At some point constraints must be put in place if the vehicle developed is too fast for the venue. An example of that would be restrictor plates in nascar racing, or in MotoGP racing, the downsizing of engines as the motorcycles exceed the safety parameters of the tracks. Unlimited aircraft racing has it's constraints also, one of them being it must be a piston driven aircraft. The governing body of America's Cup racing made a decision to not exclude multi hulled craft from its design constraints. Just like at one point they decided that 12 meters would be the maximum hull length. As I stated before, there are plenty of mono hull classes that you can still compete in if that is your definition of the purist sport of sailing.
The multi hulled designs have not exceeded safety concerns, nor is there a concern that the speeds have exceeded the safety concerns of the venues they are held in. The developments that the America's Cup bring forth trickle down to many aspects of the sport of sailing and are judged by those that make the rules to be included in allowable specifications or not. You guys meak it sound like the multi-hulls have ruined the sport and that is where we differ. They have changed the sport, yes, but there are many like me who want to see what man can do with sails, wind and water and just how far and how fast we can go with it. There is no doubt that the America's Cup is an event that brings enough excitement that the general public will turn out in droves to watch it and support it. Many of those spectators will be inspired to purchase their own craft and join in on the fun that can be had sailing all over the world.