Dude, rationalize it however you want to.
But, you can't convince me that Alta is the only ski hill in the world that has traverses and bootpacks to access terrain.
And, you can't convince me that traverses are a valid reason to ban snowboarding, because if that was the case, it would be banned from all kinds of mountains.
However, I am convinced that people like you should not be allowed to ski in terrain parks, because without snowboarding parks would not exist, and if you think that you can exclude them from your area, then they should be able to exclude you from theirs.