Nukes are only used to scare the public. In reality, precision bombing is used in war. Just think of the TV coverage of all the wars in the middle east. There is no need to obliterate a whole city, if you can take out the military capability alone.
A bullet also kills remotely, it just gets transported over an almost straight line and hits where it can be seen directly by the shooter. A killer robot moves around obstacles and the operator can see via a camera. However, a missile, grenade or mortar travels in an arc and explodes where it cannot be seen at all. So, using remote vehicles to deliver a killing blow isn't really a new idea.
Ayup, and when there is a mishap, how do you evacuate the remaining living people from a vacuum tube suspended in/over the ocean? I tend to think the proponents of this boondoggle suffers from a vacuum between their ears.