Well, aside from being a slap in the face, this is really not a huge problem. There are plenty of ships to Alaska that time of year and you should be able to rebook easily.
However, I would not let HAL know you feel that way. Go in to your Travel Agent and let her know that you are extremely unhappy and see what she can negotiate with HAL. With any luck at all you can get a Future Cruise Credit or at least a nice On Board Credit out of it.
Have a GREAT cruise!