Giving insurance companies more information simply reduces the scope of what they will insure. Highly predictable risk (I will be dead before I turn 150) is not really insurable. Unpredictable risk (I will be struck by lightning) is. Genetic screening just moves some unpredictables to the predictable column.

Is it fair? No clue. If it turns out that there's a genetic predisposition to being struck by lightning that modern genetic testing uncovers, then all those "struck by lightning" policies will die - they were subsidizing the highly conductive to the detriment of the non-conductive. Hope you're not highly conductive!