I think the big danger is not that they are hackable, but that they are thinkable.
The thing that has stopped nuclear war all these years is not the explosive power of the devices, but the long-term contamination. Nuclear war is "unthinkable" because the consequences are grave and global. The world has twice been saved by Soviet officers who elected not to follow orders and elected not to launch despite a clear indication of incoming US warheads (in one case) or the sub with weapons being directly fired upon by a US ship. If nuclear war were not unthinkable, those two officers would certainly have followed orders.
So what scares me about this option is that they are saying it has nuclear-level destructive power, but it's completely thinkable, usable, reasonable, tactical. Which means it will get used as soon as it's convenient, not just when the unthinkable option becomes the only option left.
