The music from this band is timeless and out there for everyone to enjoy. Most bands today tour to make money because no one is buying music anymore. This band has made millions and probably don't need money so badly that they have to put someone's health in danger. If they are so insistent on touring they can get another vocalist.
It is not up to us as to whether or not we should have any basis in making a decision because a band's lead singer might suffer from hearing loss. Each individual should make their own decision as to their health.
On that note total hearing loss is not a fun thing to experience. We should not be able to experience entertainment at the expense of another.
AC/DC is comprised of the individuals in the band. If one of them is unable to tour, the band should not just plug in another performer and pretend to be the same. There is really no reason to pretend to be the whole entity when core pieces of what made the band what it is are no longer able to participate.
This is horrible news in all but I mean come on you still got a show to perform for all of those who have already bought their tickets. They have technological advances that I'm sure this dude can afford to help him with his hearing loss. I think everyone will be just fine.